GENE WADDELL

CREATING THE PANTHEON

Design, Materials, and Construction

Ε «L'ERMA» di BRETSCHNEID R Ρ Interior of the Pantheon by Giovanni Paolo annini with its original attic design, c. 1750 (FU 12526F) GENE WADDELL Creating the Pantheon

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ISBN 978-88-8265-493-1 Contents

Abbreviations 9 1. Concrete 39 Preface 11 2. Proportion 39 3. Space 40 4. Enframements 40 PART I. INTRODUCTION 5. Scale 40 6. Precedents 41 1. Preliminary Considerations 15 7. Embellishment 41

A. Brief Description of the Pantheon ... . 15 8. Light 41 B. Date of Construction 17 9. Variety 42 C. Confirming the Identity of the Three 10. Permanence 42 Pantheons 21 D. Purpose of the Existing Pantheon 22 4. Concrete Construction 43 E. Main Problems to Be Solved A. Advantages 43 by the Architect 23 B. History 44 F. The Client and the Architect 23 C. Materials 44 1. Pozzolana 44 2. Major Advances in Knowledge 27 2. Aggregate 44 A. Serlio 27 D. Early Types of Facings 45 B. Palladio 27 E. The Use of Bricks 45 C. Desgodetz 28 1. Brick-faced Concrete 45 D. Francesco Piranesi 28 2. Through-courses 46 E. Leclère 29 3. Concrete Voussoirs 47 F. Lanciani 29 4. Tile Linings 48 G. Chedanne 29 F. Construction Methods 49 H. Beltrami and Armanini 30 G. Curing 50 I. Terenzio 31 J. MacDonald 31 5. General Sources of Design 51 K. Licht 32 A. Related Building Types 51 L. Wilson Jones 32 Baths 51

Tombs . 52 3. Basilicas 53 PART II. ROMAN DESIGN AND 4. Round Temples 53 CONSTRUCTION 5. Triumphal Arches 54 6. Theatres 54 3. Standard Design Procedures 35 B. Related Design Features 54 A. Vitruvius' Basilica at Fano 36 1. Domes 54 B. What the Pantheon's Architect Took 2. Internal Buttressing 55 for Granted 38 3. Attached Porticoes 56 6 6. Specific Sources of Design and 4. The Need for Models 84 Construction 57 5. Interlocking Spirals 85 A. Sources for Design Elements 57 D. Forecourt and Basilica of Neptune ... 86 1. Dome with Coffers and an Oculus 57 2. Free-standing Building with an

Attached Portico and Forecourt .. . 58 PART IV. CONCRETE CONSTRUCTION 3. Intermediate Block with Stairs 58 4. Cylindrical Drum with Solid Walls 58 9. Lower Drum and Block 91 5. Various Separate Elements in A. Site Preparatio 91 Combination 59 B. Materials and Methods 6. Proportions 60 of Construction 91 B. Sources for Structural Elements 61 1. Foundations 91 1. Dome with Steprings and 2. Walls 91 Through-courses 61 3. Vaulting 92 2. Wall Chambers Open to the Outside 4. Load-bearing Columns 94 on Multiple Levels 61 C. Surveying the Site 95 3. Concrete with Horizontal Layers Preparing Foundations 95 of Graded Aggregate and Construction Methods Used for the Through-courses 62 Lower Two-thirds of the Drum and 4. Concrete Voussoirs 62 Block 95

5. Concrete Vaults with Tile Linings . 62 1. Lower Section 95 C. Unparalleled Features of the Dome ... 62 2. Middle Section 97

10. Upper Drum and Block 99 PART III. PRELIMINARY DESIGN PHASE A. Upper Third of the Drum 99 1. Exterior 99 7. The Site 67 2. Spaces Within the Drum 100 A. Site Selection 67 3. Buttress 100 1. 67 B. Upper Block 100 2. Vicinity 67 1. Exterior 100 B. Orientation 68 2. Rooms 101 C. Relative Altitudes 68 3. Stairs 102 D. Existing Conditions 71 1. Agrippa's Foundations 71 11. Dome 103 2. Other Existing Conditions 73 A. Lower Dome 103 1. How the Dome Could Have Been 8. Structural Design 75 Constructed 103 A. Plan 75 2. Steprings 104 1. Proportions 75 3. Materials 105 2. Circular Plan 77 4. Constructing the Coffers 106 3. Exedras 78 B. Upper Dome 106 4. Interior Attic 79 C. Oculus 106 5. Transitional Block 79 D. Steps 107 B. Elevations 81 E. Bronze Roofing 107 1. Proportions 81 F. Cracks in the Dome and Walls 107 2. Exedras 81 G. Conclusion 109 3. Exterior 82 C. Coffers 83 Alignment 83 PART V. EMBELLISHMENT Precedent 83 The Need for Computation 84 12. Comparisons of the Orders 113 7 Α. Proportions 113 Bibliography 165 Columns 113 Index 177 Intercolumniations 116

Plans 117 Entablature 118 ILLUSTRATIONS Β. Materials 120 Differences Between the Interior and Frontispiece: Pannini's View of the Interior of the Portico 121 Pantheon Construction 121 1. Photographs of the Pantheon 13. The Porticoes 123 General views, pls. 1-7 Α. Architectural Evidence 123 Details, pls. 8-29 1. Description of the Present Portico 123 Construction, pls. 30-48, 49Β 2. Structural Relation of the Portico Comparable Hadrianic Sculpture, pls. 49Α, 50 to the Block 124 -55 Β. Archaeological Evidence 126 C. Further Evidence of Change 128 2. Drawings and Prints of the Pantheon 1 Inscription 129 Peruzzi to Dosio, c. 1490-c. 1569 2. Entrance 129 Peruzzi and others, c. 1490-c. 1535; pls.

3. Upper Block 130 56-58, 60B, 70 4. Pediments 130 Heemskerck, 1535-1536; pls. 59-60 Α 5. Reuse of Material 132 Serlio, 1540; pl. 61 6. Solecisms 132 Dosio, c. 1550-1569; pl. 62 7. Later Buildings Influenced by the Palladio, c. 1550-1570; pls. 63-69 Pantheon 133 Desgodetz, 1682; pls. 71-73 D. Proposed Explanations for Changes 134 Piranesi, c. 1750-1790 Some Early Explanations 134 G. B. Piranesi, c. 1750; pls. 74-75 Sixty-foot Columns 135 Francesco Piranesi, 1790; pls. 76-104 E. Conclusion 135 Fea to Lanciani, 1806-1892 Fea, 1806; pl. 105E 14. Finishing 139 Leclère, Choisy, and others, 1813-1873; 105Α, 106 Β A. Main Story 139 -111, 115 Exedras 139 Lanciani, 1882-1901; pls. 112-113 Aedicules 140 Middleton, 1892; pls. 114-115 Α Wall Facing 140 Chedanne, Beltrami, and Armanini,

B. Attic Story 141 1891-1898; pls. 116-125 C. Floor 141 Gismondi to Terenzio D. Color Combinations 143 Gismondi and others, 1927-c. 1930; pls. Β E. Dome 143 126-127, 132 -133 Interior 143 Beltrami, 1929; pls. 128-129 Exterior 143 Terenzio, c. 1932; pls. 130-132 Α F. Furnishings 144 Licht to Wilson Jones; 1966-2000 G. Drum Exterior 144 Licht, 1966; pls. 134-137 H. Block Exterior 145 Pelletti, 1989, and others; pls. 138-139, 144, 145Β I. Entrance 145 J. Portico Ceiling 146 Wilson Jones; 2000, pls. 140-143, 145Α K. Sculpture 146 L. Forecourt 146 3. Comparable Buildings A. Republican Period, 500-29 BC Conclusions 149 c. 100 BC, Round Temple by the Tiber, Notes 151 pl. 146E c. 80 BC, Temple of Fortuna, 8 147Α Praeneste (Palestrina), pl. c. 80 BC, 189, 196, 200-201, 209E Β Round Temple at Tivoli, pls. 147B-148 c. 130, Temple of Venus and

Augustan Period (29 BC-14 AD), c. 30 (largely completed in. c. 135; platform 148Β 28 BC, Basilica at Fano, pl. BC, survives; rebuilt c. 307), pl. 202-203

Mausoleum of (first used), C. 130, Hadrian's Library, Athens, pl.

pl. 149 c. 25 BC, Tomb of Caecilia 204-205Α

Metella, pl. 150 16 BC, Maison Carrée, c. 130, Triumphal Arch at Antinoopolis, 151 Α 205Β pl. c. 11 BC, Theatre of Marcellus pl.

(completed; begun c. 44 BC), pl. 151B C. 130-139, Hadrian's Tomb and Bridge Α 2 BC, Forum of Augustus completed (Pins Aelius), pls. 206-209

(including the Temple of Mars Ultor), C. 130, Temple of Trajan and Plotina, pl.

pls. 152-156ΑΑD 6, Temple of Castor 210

and Pollux (rebuilt), pl. 156B 10, Temple c. 130, Hadrianic Buildings at Ostia, pl. 157Α 10 of Concord , pl. -27, Triumphal 211 158Α 38 Arch at Orange, pl. -c. 50, c. 130, Other Hadrianic Buildings at

Aqueducts and Temple of Mercury, Baia, Rome and Baia, pls. 212-214

pl. 158-159 Antonins Period (AD 138-193)

Nero and the Flavians, AD 54-96 c. 64, c. 138, Temple of the Deified Hadrian 161 Α 215Α 140, Nero's Aqueduct, pl. c. 64, Nero's (Hadrianeum), pl. Temple of

Golden House (Domus Aurea), pls. 161 B- Faustina (dedicated also to Antoninus

162 Pius in c. 160), pl. 215B

70-80, Colosseum (interior and upper Severan Period (AD 193-235), pls. 216-

story largely rebuilt from c. 217-240; 222 Α often repaired), pls. 163-165 c. 80, c. 203, Arch of Septimius Severus, pl. 6Α Flavian Amphitheatre, Pozzuoli, pl. 165E 2 1

C. 90, Domitianic Baths at Albano, pls. C. 203, Portico of Octavia (reconstructed Α 166-167 c. 90, Domitíanic Great Hall, by Septimius Severus and Caracalla), pls.

Roman Forum, pl. 167E 216E-217

Trajanic Period, AD 98-117 211-216, Caracalla's Baths, pls. 218-221

104-109, Trajan's Baths, pls. 168-174 c. 230, additions to Agrippa's Baths by

107-112, Trajan's Forum (with the Alexander Severus, pl. 222

Basilica Ulpia and Trajan's Column, pls. c. 230-240, Round temple at Ostia, pl.

175-177 223, 224E

107-110, Trajan's Markets, pls. 178-184 Diocletian and Maxentius, AD 284-312

C. 110, Trajan's Arch at Beneventum, pl. C. 300, Temple of Minerva Medica

185 (Licinii garden pavilion), pls. 226-227

Hadrianic Period, AD 117-138, pls. 186- c. 300, Tor de' Schiavi, pls. 228-229

213 c. 123-130, Hadrian's Villa, pls. 186- 305-306, Diocietian 's Baths dedicated

201 (eventually renovated as S. Maria degli Β Serapaeum, pls. 190-191 Angeli), pls. 230-232, 233 Α Roccabruna, pls. 192-194 306, Basilica Nova (largely built by

c. 126, Piazza D'Oro Vestibule, pls. Maxentius; reoriented by Constantine), Α, 234 1 94B- 195 pls. 233 -235

c. 126, Small Baths, pls. 197 c. 307, Temple of Venus and Rome Α, 198 Α C. 129, Large Baths, pls. 197 -199 (rebuilt by Maxentius), pls. 236-237 Α c.123-c. 138, Misc. Other Buildings, pls. Miscellaneous, pls. 237 -240 Abbreviations

AAR—American Academy in Rome JSAH—Journal of the Society of Architectural Historians

AJA—American Journal of Archaeology MAAR—Memoirs of the American Academy in Rome

BComm—Bullettino della Commissione Archeologica Comunale PBSR—Papers of the British School at Rome di Roma QuadIStA—Quaderni dell'Istituto di Storia dell Architettura CIL— Corpus Inscriptionum Latinarium (Dresse11891) RM—Mitteilungen des Deutschen Archäologischen Instituts: EUR—Museo della Civiltà Romana, Esposizione Universale di Römische Abteilung Roma S. A. R. A.—Società Aerofotografie e Rilevamenti FU—Fototeca Unione (American Academy in Rome) Aerofotogrammetrici

GW—illustrations owned by the author SBAAL—Soprintendenza ai Beni Ambientali e Archittonici di Lazio (which in 1990 divided its architectural photographs into ICCD—Istituto Centrale Per il Catalogo e la Documentazione separate groups for Lazio and Rome and transferred the Rome (ICCD; Fototeca Nazionale, Ministero per I Beni e le Attività photographs to SBAPCR. In the 30's all of Lazio including Rome Culturali; including the Aerofoteca or Laboratorio per la was under the Soprintendenza Monumenti del Lazio.) Fotointerpretazione e la Aerofotogrammetria) SBAPCR—Soprintendenza per i Beni Architettonici ed il JRA Journal of Roman Archaeology Paesaggio per il Comune di Roma (including architectural photographs created for the Soprintendente aí Monumenti del JRS—Journal of Roman Studies Lazio; cf. SBAAL) Preface

This book is about everything that was required to create the ed. On the basis of this knowledge, I have attempted to recon- Pantheon. It covers the design and construction of the building, struct how it was designed and how it was intended to look. and it includes information on sources of design, methods of de- I have considered the stages of design and construction in the or- sign, materials, and methods of construction. der in which decisions needed to be made. Every decision has been In addition to being one of the most influential buildings ever considered from the point of view of the architect in an attempt to created, the Pantheon is one of the most controversial. Every as- determine what he could have learned from earlier buildings, what pect of its design and construction has been a subject for scholarly he was attempting to accomplish, what decisions he needed to make, debate, and many continue to be. Various scholars have dated it what options he had, why some options were preferable, what prob- from c. 25 BC to AD 180. Its portico has been called definitely lems arose during construction, what vestiges of redesign are present, original and unquestionably added. Its purpose has been consid- and why redesign was sometimes necessary. Although some design ered sacred and secular. Its dome has been said to rely primarily sources may not have survived, some buildings constructed shortly for support on brick ribs and to be monolithic. Its interior col- before have so many of the same features that they are likely to have umns are thought to be structural or decorative. The facing of the been directly influential, and they help to reconstruct how the Panthe- attic story was removed for having been supposedly added yet was on was designed and constructed. an integral part of the overall design. For poorly documented buildings, a sequence of numbers A great deal is still unknown about the Pantheon. There con- must be reconstructed that is capable of generating all major di- tinues to be disagreement about whether or not some parts such mensions. Since architects design using numbers, architectural as the portico are original. Little archaeological work has been historians have to understand how and why specific numbers were done, and what has been done continues to be reinterpreted. Al! used to be able to reconstruct a design process correctly. To de- of the building has never been thoroughly and systematically ex- termine this, it is necessary to consider dimensions in Roman feet amined to determine how parts of it were constructed. Most of (0.296 meters), and unless otherwise indicated, all dimensions that the upper surface of the dome has not been uncovered in centu- are given in feet are in Roman feet.' ries. Cores have never been taken to determine if brick arches ex- To reconstruct the design of the Pantheon, I have tried to ex- tend entirely through the walls. Despite many uncertainties, more amine every surviving building that might have influenced it. I than enough is known about the building and about closely related used an approach similar to the one that was necessary to deter- buildings for conclusions to be reached that are likely to be con- mine how the Parthenon was designed. 2 What the architects of firmed. What is concealed beneath the surface of the largely in- the Parthenon were attempting to accomplish could only be de- tact building can be inferred with a high degree of probability on termined by comparing all 43 of the best preserved Greek Doric the basis of a careful examination of the parts that are accessible temples that have peripteral plans. This was the only way to re- and on the basis of numerous comparisons with buildings that are construct a design process capable of generating the dimensions in many respects similar. needed at each stage of construction for the great majority of these For any building as poorly documented as the Pantheon, it temples. Similarly, how the Pantheon was designed required tak- is necessary to make a thorough examination of the building it- ing into consideration all evidence about the building itself and self. For three decades, I have examined most parts of the build- related buildings and accounting for all of it. ing carefully and repeatedly. At various times, I have been able Hundreds of books and articles have been written about the to visit every type of space in the drum, Transitional Block, and Pantheon, and a large part of them attempt to prove mutually ex- adjacent grottoni. I have been on the roof and within the walls. clusive theories. My conclusions rely to a large extent on the in- I believe I have been able to determine what parts are o riginal, sights of earlier writers, but by using a more comprehensive and which were added at various times during a period of nearly two systematic approach, I have reached significantly different con- thousand years, and how all parts of the building were construct- clusions that account more fully for the available evidence. 12

Acknowledgements Part of the research in Rome was made possible by sabbati- cals provided by the Getty Center for the History of Art and the My greatest debt is to studies of the Pantheon by Kjeld Humanities in 1991 and by the College of Charleston in 2007- de Fine Licht and by William L. MacDonald. Much of what is 2008. Four travel grants from the College of Charleston Library known about the building was assembled by each of these schol- and a Provost's Grant enabled me to spend nearly a year and a ars independently and at about the same time, publishing their half in Rome to examine all relevant buildings thoroughly and to principal works in 1965 and 1966. Together they provided an in- do research in ancient design and construction methods. David valuable basis for the study of all aspects of the Pantheon. Cohen and Marie Ferrara have supported my research by provid- Licht's magnificent monograph has great and permanent ing flexible work and vacation schedules and by approving re- value. No other study is as comprehensive or as well ilustrated. search leave and a sabbatical. I have cited his book far more frequently than any other, and my I am grateful to Will Evans and Joe Schmidt of Evans & debt to him is greatest of all. However, he used a different ap- Schmidt, Architects, who made a generous contribution to the proach and came to many conclusions that I have been unable Friends of the College Library that helped to fund this publica- to accept.3 Rather than starting with the foundations, he started tion. John M. Rivers, Jr., helped greatly to make this book pos- with the portico and worked his way from north to south and to sible. the basilica behind the Pantheon. He might well have reached John Poindexter read and commented on the entire text and different conclusions if he had considered the problems that had improved it in innumerable ways. Mel Smith has provided good to be solved in the order in which they needed to be solved. He advice for many years. Katina Strauch urged me repeatedly to presents a large number of the most important sources of design, apply for a sabbatical to complete this study. Their friendship but only after he discussed the building. and encouragement have been indispensible. MacDonald's section on the Pantheon in his seminal study Many items in the bibliography were made available of the development of Roman architecture gave further consider- through the Interlibrary Loan Department of the College of ation to specific sources of design and to how the Pantheon fits Charleston, and I owe a great debt to Mike Phillips and his high- within the context of Roman architecture as a whole. After eval- ly eftícient staff. The rarest titles were available at the American uating the same and some other sources for the building's de- Academy in Rome, the Deutsches Archäologisches Institut, the sign and construction, I reached somewhat different conclusions Biblioteca di Archeologia e Storia dell'Arte, and the Biblioteca about how and why they were important. What he wrote about Hertziana. the building's construction has been largely superceded, but his Historic photographs have been provided primarily by the writings have had great influence and continue to be essential Soprintendenza per i Beni Architettonici ed il Paesaggio per il reading for the Pantheon and for Roman architecture. His later Comune di Roma (including photographs of Roman buildings book on the Pantheon has long provided the best overview of its created for the Soprintendente ai Monumenti del Lazio); by the place in the history of world architecture. 4 Istituto Centrale Per il Catalogo e la Documentazione (ICCD; A forthcoming collection edited by Mark Wilson Jones and Fototeca Nazionale, Ministero per I Beni e le Attività Culturali; Tod Marder for Cambridge University Press will add further to including the Aerofototeca or Laborato rio per la Fotointerpre- what is known about the impact of the Pantheon and will also tazione e la Aerofotogrammetria); and by the Fototeca Unione add to what has been discovered about the building through re- (American Academy in Rome). Nearly all photographs taken by cent studies. My chapter on specific design sources was adapted Alinari, Brogi, and Anderson are from original albumens that I from an article prepared for their volume. have been able to acquire through many years of collecting. I have often had the benefit of discussing the building on For access to areas of the Pantheon that are ordinarily inac- site with the architect Randolph Martz and the architect and ar- cessible, I am grateful to Armando Schiavo, Architect and Presi- chitectural historian Mark Wilson Jones. Mark has also provided dent of the Pontificio Accademia dei Virtuosi al Pantheon; Gi- a great deal of constructive criticism for the chapters on design usseppe Simonetta, Architect; Marco Bernardi; and Giovanni sources and on the portico. Belardi, Architect and Director of the Pantheon. Chapter 1: Preliminary Considerations

(lA) Brief Description of the Pantheon proportions and measurements divisible by five or ten were char- acteristic of imperial Roman architecture. The Pantheon consists of a cylindrical drum, an integral Tran- The interior wall is divided into two levels, and above its sitional Block, and an attached portico (pls. 1 & 4). The Transi- foundation the exterior wall is divided into three levels (pl. 130). tional Block is located in between the drum and the portico, and it Two of the three levels of the exterior correspond to the interior. will usually be referred to simply as the Block (pls. 3 Α & 77-80). The exterior has an additional story at a higher level. The founda- The drum and Block share the same foundation and were initially tion has a brick facing for about 7 of its 15 feet that was evidently connected to one another, and they were thus largely constructed intended to be exposed to the weather, but has been largely con- at the same time. The portico was constructed soon afterwards, cealed by silt. The taller attic of the exterior starts at the level of and it rests partly on foundations of the earlier building that had the springing of the dome, and it resembles the surcharge of many been constructed on the site by Agrippa. There are many indica- domes, but like the lower stories of the drum, it contains numer- tions that the portico was redesigned both before and after the rest ous chambers that lightened rather maximized its weight. of the building was completed. Although the drum and Block began to be constructed to- Α basilica on the south side of the Pantheon was built at the gether, they began to be constructed separately at the level of the same time as the drum and was connected to the south side of the barrel vaults over the entrance. The entrance consists of two bar- drum by a buttress. This "bridge" stabilized the clearstory of the rel vaults with different heights. The barrel vault inside springs basilica, which was initially an entirely separate building (p1.48). from an entablature supported by columns 36 feet tall and outside Α series of narrow rooms (the grottoni) were later constructed in above columns that are 48 feet tall. The relative difference in the between the drum and the basilica (pl. 131). height of these columns is 3:4 (both dimensions being divisible by What is evident from the materials and methods of construc- 12). The barrel vault on the inside is part of the drum alone, and it tion has been largely confirmed by brickstamps. The rotunda, extends upward and cuts through the attic story (pl. 85). The bar- Block, and basilica were built at the same time, and they were rel vault on the outside is entirely a part of the Block, and the rest constructed during the reign of Hadrian, but partly of mate rial that of the Block was constructed separately from the drum. had been manufactured earlier. The grottoni were added later, but Opposite the entrance is an apse that is four feet wider and are also Hadrianic. The foundations for the present portico were that has a semi-dome. The entrance arch and the apse establish a almost certainly added during the Hadrianic Period, but since strong axis from north to south, and this is the principal axis of the they are level, they were inserted after the stone foundations of building. This axis was further emphasized by columns that flank Agrippa's Pantheon had been reused for the Block and had settled the apse and by other design features including the orthogonal pat- unevenly. tern of the floor and the coffer pattern of the dome. The interior of the rotunda is 150 Roman feet in diameter and On the cross axis (to the east and west) are large, semi-circu- in height (frontispiece). The Block is square and overall is 108 lar exedras with the form of apses, but their semi-domes are con- feet in height and width. cealed by the attic. These two exedras and four others are fronted The interior walls are half of the total height of the interior; by columns in antis, and the diagonal axes (southeast, southwest, the dome rests on a cornice that is 75 feet above the floor, and the northeast, and northwest) have similar exedras, making a total of dome itself is also 75 feet high. The interior drum and dome thus six exedras and eight openings in the main story. The entrance is relate to one another as 1:1, and each relates to the overall height two-feet narrower than the exedras and the apse two-feet wider. as 1:2. The interior drum is subdivided into a main story that is The four exedras on the diagonal axes have straight sidewalls and 45 feet high with an attic story that is 30 feet high, and the attic barrel vaults (rather than half-domes), and these barrel vaults are relates to the main story as 2:3. also concealed by the attic. The principal ratios used to design the interior and exterior of There are eight broad structural piers in between the eight the Pantheon are the simple ones of 1:1, 1:2, and 2:3. The princi- major openings of the interior, and attached to the front of these pal dimensions divide evenly by 5, 10, 25, and/or 50 feet. Simple piers are aedicules that resemble small porticoes. The pairs of 16

aedicules flanking the two main axes on the cardinal points have entrance (pl. 131). There are a total of 16 columns and 4 piers, triangular pediments. The pairs of aedicules flanking the diagonal and the piers are adjacent to the Block. The outer columns m i- axes have pediments with segmental arcs. The materials used to tially all had shafts made of gray granite; the inner columns have construct these two sets of aedicules also differ and further distin- shafts of red granite; and the piers have shafts of white marble. guishes one set from the other. These elements are arranged to create three distinct spaces: a

The attic story of the interior has 14 windows. There is a broader space opposite the entrance (three interaxials wide) and window above every exedra and above every aedicule, but none two aisles that align with the apses on the front of the Block. above the entrance and apse. The six windows above the exedras The columns across the front of the portico rest on travertine function as a clearstory that allows light from the oculus to enter foundations that survived from a previous Pantheon (pls. 118- the tops of the exedras (frontispiece). The eight windows above 121). These stone foundations are very nearly 150 feet across (the the structural piers are false windows that were added to maintain width of the interior of the rotunda), and since the portico is 108 a regular pattern, but behind these false windows are wall cham- feet across, the sidewalls of the stone foundation extend roughly bers, and they originally opened into these chambers at least until 20 feet beyond each side of the portico. These earliest surviving the concrete had cured; all other wall chambers have openings to foundations are located well below the present ground level and the outside. Centered on all 16 openings in the attic are flank- are not visible; these rectangular foundations were discovered dur- ing pairs of pilasters (the bases of which were cut through by the ing the only major excavations of the Pantheon that took place in arches of the entrance and apse). the late 19th Century.

The dome has a single oculus 30 feet in diameter at its apex, The columns of the front of the portico rest on the north and this opening is one-fifth of the overall diameter. It provides side of these pre-existing stone foundations, and the front of the the principal light for the interior, but light also enters through the Block rests on the south side. Within the rectangle of stone were entrance, which is equivalent in size, and the doors were undoubt- inserted four foundation walls of shuttered concrete to support the edly kept open at least when trials were being conducted; Roman portico's four rows of columns and piers. These inner founda- trials were open to the general public. The surface of the dome tions were constructed within wooden formwork that left board has five rows of 28 nearly trapezoidal coffers for a total of 140 impressions. Since the foundations of shuttered concrete were not coffers. Each coffer is subdivided into a series of increasingly pulled down with the stone foundations when the Block and drum smaller and deeper coffers, and the corners of the coffers align settled, they were added after the construction of at least much of and create the impression of interlocking spirals. the body of the building (p1. 121).

The exterior of the dome has a recessed vertical wall at its The present portico was constructed with columns that have base that resembles a podium. Above this wall are six concentric monolithic granite shafts, and the piers were made of marble steps or steprings, and above the set of steprings is a saucer dome drums (segmented). The columns and piers have marble bases

(p1. 4Β). and capitals, and marble was used for the entablatures. Brick

The Transitional Block is an essentially hollow structure with arches on stone pedestals were used to support the roof structure Β). roughly triangular stairwells at each end. On its front is a pair of (p1. 14 The existing marble trim of the portico and Block is apses flanking the entrance (pls. 130 & 75). In the center is the mitered in ways that indicate that the existing marble trim was larger arch of the front entrance. The foundations of the Block created at the same time. The roof structure originally consisted and of the drum within the portico were made of concrete without of bronze roof trusses, which were replaced with wood. a facing and without the use of formwork; the concrete was sim- The walls of the drum are about 20 feet thick, and like the ply laid up in thin layers within a trench that had been dug through Block, they are largely hollow (pls. 77-79). In addition to the eight alluvial clay. The walls of the drum have no facing on the interior, major openings in the main story of the interior, there are eight ap- but they have a brick facing on the exterior. Small amounts of sidal chambers within the walls with a chamber behind each aedi- opus retículatum (a tufa facing) have been found at the base of cule. The attic story of the drum is similarly hollowed out by the the south side, but nowhere else. The absence of a facing in front concealed barrel vaults above the six exedras in addition to a visible of the Block indicates that some kind of portico was planned to barrel vault above the entrance and a semi-dome above the apse. protect the north part of the foundation. Above the east and west exedras are half-domes. Above the four The rotunda was initially covered with bronze roof tiles. Af- exedras on diagonal axes are curving barrel vaults, each of which ter being stolen, the tiles were eventually replaced with lead, large is subdivided by two smaller arches running from front to back. In quantities of which had been used by the ancient Romans for wa- between the arches of the exedras is another set of apsidal chambers ter pipes. at the attic level that align with the lower set of chambers (p1. 78). The present portico has a tall pediment supported by eight On the exterior, the uppermost part of the drum that conceals the columns in front and four columns or piers on the sides with two base of the dome contains sixteen chambers that correspond in posi- additional internal columns and a pair of piers to either side of the tion to lower chambers or vaulted openings in the walls (p1. 79). 17 The interior of the nearby basilica to the south of the Panthe- or group of buildings? A. C. G. Smith later confirmed that the on is 150 feet long (like the interior of the Rotunda and the width Pantheon is contemporary with Hadrian's Villa.' of the stone foundations of the earlier Pantheon; pl. 76). Although Bloch's summary of Guey's evidence indicated that of 120 dat- this basilica was begun as a separate structure, it was later con- able stamps found in situ in the Pantheon and adjacent grott οni, 115 nected to the top of the Pantheon's drum. An integral projection were probably made during Hadrian's reign (AD 117-138) 4 Bloch that survives on the south side indicates that the Pantheon was concluded that the Pantheon was constructed during the first half of intended to buttress the Basilica of Neptune (pls. 48 & 82-83). Hadrian's reign beginning around 118 or 119, when Hadrian was first Clearstories were often buttressed, and a smaller clearstory cannot in Rome after becoming emperor, and is likely to have been dedicated have been expected to have buttressed a larger dome. from 125 to 128, when he was again in Rome. After at least the walls of the Pantheon and the Basilica of Some aspects of the evidence of brickstamps are controver- Neptune had been completed, eight parallel walls was constructed sial, and insufficient consideration has been given to the strati- on entirely separate foundations in between the two buildings. graphic significance of the specific locations of finds. There is The foundations of these walls are shuttered concrete like the no question, though, that most of the building including its dome foundations for the inner columns of the portico, and the walls is Hadrianic rather than Augustan, Trajanic, or Severan. There is that rest on them are concrete faced with brick that have stamps good reason to believe that the interpretations of the evidence of dating from the Hadrianic and Severan periods. The walls were brickstamps by Guey, Bloch, and Smith are correct and that the constructed during the Hadrianic Period, and arches in the walls building was wholly constructed during the Hadrianic Period. were reinforced during the Severan Period. This evidence will be discussed in detail later in this section. Concrete, brick, stone, and bronze were used to create a fire- The evidence relating to the date of the portico is still more proof building on the site of two earlier Pantheons that had both difficult to determine than for the drum and Transitional Block burned. The Rotunda was centered axially in relation to the pre- since its columns rest on shuttered concrete rather than on con- existing stone foundations, and the front of the portico aligns with crete made using bricks that can be dated, but the evidence as a these foundations (even though they are 5 degrees west of North whole favors a Hadrianic date: Identical foundations used for the rather than correctly oriented). Considering that the portico aligns grottoni support brick-faced walls with Hadrianic brickstamps. with the front of these stone foundations, that the interior of the Large monolithic columns of Egyptian granite began to be used Rotunda has the same width and orientation as these stone foun- widely around the beginning of the 2nd Century AD rather than dations, and that the name of the building and of its initial builder during the Augustan Period. Only the stone foundations of the were reused, the existing remains on the site can be considered the portico are probably Augustan. If Domitian had built new foun- starting point for the design. dations, they would probably have been made of concrete, which he used for his nearby stadium and for his palace on the Palatine The number of years required to construct the Pantheon is (1B) Date of Construction uncertain, but a more crucial factor was how long concrete needed to cure rather than how many workmen could be employed at one To be able to distinguish a potential source (an earlier build- time. Some parts of the walls are about 20-feet thick, and since ing) from a parallel example of influence (a later building), it is thick layers of concrete had to be given more than sufficient time necessary to indicate with as much precision as possible when the to set up in order to support additional layers, the construction of Pantheon was constructed. There has been much disagreement the building probably took at least several years. about when the Pantheon was constructed, and its dates continue This estimate of the time required is comparable to the num- to be disputed. ber of years known to have been needed to construct other large For 17 centuries, from around AD 200 until 1882, the inscrip- buildings primarily of concrete. For example, the Colosseum was tion on the frieze of the existing building stating that Agrippa built constructed from AD 70-80 (p1. 164), Trajan's Baths from AD it was taken at face value. A study of brickstamps by Chedanne 104-109 (pl. 168), and the Baths of Caracalla from AD 211-216 indicated, though, that all parts of the building were constructed (p1.218).5 Since the Pantheon was a smaller project, it may have using bricks that were made during the reign of the Emperor taken less than five years to build, but considering that its walls Hadrian or shortly before. Chedanne's research was confirmed by are so much thicker than usual even for large buildings, the walls the excavations of Beltrami and Αrmanini.' needed an unusually long time to cure before they could securely Brickstamps had been recorded from the Pantheon as early as support the immensely heavy dome. The length of time that was the 18th Century, but their full significance was not realized (pls. considered necessary for concrete to develop sufficient strength to 103-104). All of the evidence available to 1936 was reviewed in support vaulting could well have been several years. detail by Guey, who found that more brickstamps from the Pan- Like other building materials, bricks seem to have been given them occur at Hadrian's Villa than in any other major building time to prove their soundness. Vitruvius wrote: 18 with regard to burnt brick, nobody can tell offhand whether it is constructed during the three years before it was dedicated. Later, of the best or unfit to use in a wall, because its strength can be he added that "within the Serapaeum and its precinct, to be sure, tested only after it has been used on a roof and exposed to bad brick-stamps of 123 are in the overwhelming majority, but a [sin- weather and time—then, íf it is good it is accepted. If not made gle] stamp of 124 (S. 98) appears in the cella wall in a place which of good clay or if not baked sufficiently, it shows itself defec- tive there when exposed to frosts and rime. Bricks that will not cannot possibly be a latter addition. " 12 One other stamp dated 125 stand exposure on roofs can never be strong enough to carry its was found in the street entrance, and two stamps dated 126 were load in a wall. Hence the strongest burnt brick walls are those found in what is "unquestionably an addition to the somewhat which are constructed out of old roofing tiles.' higher structure behind" the temple. Not a single stamp later than 124 and only one that was dated 124 was found in the temple ded- Vitruvius stated that even stone needed to be stored for two years icated at the beginning of 127. Although Bloch himself insisted before using,' and Pliny stated that lime should not be used for that the street entrance was surely constructed before the temple three years. 8 Wood was also allowed to dry for long periods be- was dedicated, he indicated that this was a conjecture. Regardless fore being used. Considering the lack of control in the quality of of whether or not this was the case, he concluded that "We shall production that is reflected in Vitruvius' distrust of bricks, they too therefore be allowed in the future to be more confident in assign- must have been set aside until it could be determined if they were ing buildings in which great masses of brick-stamps of 123, 124, likely to weather well. Although bricks are now used as soon as and 125 occur to the period immediately following these years, they have been fired, they are made of clay that has been tested that is to the years from 126 to 128." He did not think that bricks chemically, that has been mixed uniformly, and that has been fired were used in the year they were manufactured, and in fact, he spe- at a consistent temperature, and random samples are tested for cifically states that there was an average of a three-year delay in compressive strength. Having none of these methods to ensure their use. Lancaster found definite evidence that some bricks in uniformity, the Romans had to rely on how well each batch of the same level at Trajan's Market were used about a decade or bricks weathered. more after being manufactured, and she also found that five dif- Bricks were sometimes used long after having been manu- ferent brickstamps were used for one set of rooms, a circumstance factured, and the reasons include lack of demand and stockpiling that "would suggest they had been stockpiled together. "' 4 to wait for better prices. Some bricks were also salvaged from Bloch gave special consideration to why 13 dated brick- buildings that had burned and were reused. It is necessary to con- stamps found in the Pantheon were manufactured by Lupus dur- sider as many bricks as possible and to evaluate every brickstamp ing the Trajanic Period. 15 "It was the high official of the Emperor from any building that is being dated. As Lanciani cautioned: Trajan, Marcus Rutilius Lupus, who in 110 A.D. first dated his stamps. From 114 to 117, while he was viceroy of Egypt, he When we examine, for instance, the grain warehouses at Os- tia, or Hadrian's villa at Tivoli and find that their walls have resumed this practice, obviously in order to control the brick never undergone repairs, that their masonry is characteristic of production of his estates more easily during his absence."" He the first quarter of the second century, that their bricks bear the added that "the example which Lupus gave for the organization dates of Hadrian's age and no others, we may rest assured that of brick production was soon imitated. In the year 123, almost all the stamps speak the truth. Their evidence is, in such a case, brick producers of Rome marked their bricks with dated stamps, conclusive. But if the bricks are variously dated, or bear the probably also for fiscal reasons...."" In a later publication Bloch names of various kilns, and not of one or two only, then their noted, "my interpretation that he [Lupus] must have disposed of value as an evidence of the date of a building is diminished, if considerable reserves from all four years [114-117] upon his re- not lost altogether. 9 turn from Egypt still stands and has not been upset by later ar-

In the case of the Pantheon, "the bricks are variously dated" and chaeological discoveries. " 18 Thus, the small number of bricks "bear the names of various kilns," and the evidence as a whole found in the Pantheon that were manufactured during the Trajanic has to be evaluated rather using any portion of it that might seem Period can be accounted for by the usual delay in their use to en- to be more reliable. Even bricks that have the names of consuls sure that they had been tested sufficiently against the effects of and that can be dated to the year they were manufactured cannot weathering. In addition, he pointed out the likelihood that they be taken at face value unless they occur in sufficient numbers by were stockpiled during the Parthian War (AD 113-116) in order to themselves, and even then the bricks are unlikely to have been get a better price after the war ended. used for at least several years after being manufactured. Heilmeyer interpreted the Pantheon's brickstamps as indicat- Archaeological evidence provides confirmation that bricks ing that the building was begun during the reign of Trajan, but he were ordinarily used several years after being made. Bloch states consistently preferred the earliest possible date that a brick could that the Temple of Serapis, Ostia, was dedicated 24 Jan. 127. 10 have been manufactured rather than, like Block, taking an aver- Its walls "...seem to be faced almost entirely with bricks of Julius age within a range of possible dates as more likely than either Lupin made in 123...."" Thus, the temple was "almost entirely" extreme. Heilmeyer noted that only two brickstamps definitely 19

post-date Hadrian's reign, and renovations by Antoninus Pius and that "the fundamental rule for the chronology of brick structures ο Septimius Severus are d cumented. 19 is this: the thinner the bed of cement between the layers of bricks,

Bloch asked the question, "Why were bricks dated? He the older the structure."23 In general, Hadrianic brickwork (AD did not know why they suddenly began to be dated, stopped be- 117-138) is characterized by bricks that are even in their thickness ing dated, and resumed being dated. He wrote, "Axel Βο thius and by mortar joints about a third as thick as the bricks. Severan in a kind and generous review of my original work on Roman brickwork (AD 193-235) can usually be distinguished from Hadri- brick-stamps and at the same time in an article in Eranos sug- anic, and it is characterized by uneven bricks with mortar joints gested that the dates were used to assure the buyer that the bricks about half as thick as the bricks. Brickwork dating from as late had seasoned enough. This hypothesis was inspired by Vitruvius' as the reign of Diocletian (AD 284-305) can be more readily dis- recommendation for testing baked bricks by using them for some tinguished from much earlier brickwork by its use of mortar joints time as roof tiles and thus exposing them to the weather." 20 that are about half as thick as the bricks, and Christian repairs Bricks were not made during the Augustan period specificai- have joints about as thick as the bricks. Finer distinctions than ly to face concrete. Tufa was largely used as a facing, and when these are difficult to make. bricks were used, they were roof tiles that had been salvaged as Hadrian became emperor on 11 August 117, but he was in when buildings were pulled down to be replaced or had been Antioch when Trajan died, and he did not arrive in Rome until burned in one of the numerous fires that destroyed large parts of nearly a year later in July 118. 24 He was in Rome from 118-121, Rome. Roof tiles were cut down, and their edges were ground and it was during this period that he probably arranged for the flat for reuse. When brick were found to weather better than tufa, manufacture of a large number of bricks in AD 123 to provide far bricks began to be manufactured specifically to be used as a fac- greater quantities of brick for the numerous buildings he wanted ing for concrete.21 to create. More bricks have been found dating from this year than In his summary of the brick industry, Bloch notes that dated from any other. stamps were used "frequently between 110 and 164 AD," but rare- Only two bricks dated AD 123 have been found in the Pan- ly afterwards: theon, and considering that nearly 200 brickstamps have been found there, so small a number dating from this year is undoubt-

It is difficult to see why producers would have stopped using edly significant. The Pantheon must have been largely completed stamps if they had been useful to them, but in any case there by AD 126 or it would have more bricks dating from AD 123. If was little consumption between 164 and about 298, and the a fragmentary stamp identified as dating from AD 123 actually brick industry came to be so entirely owned by the emperor came from about one meter above the floor of the Pantheon, the that controls could be applied more effectively without relying rules of stratigraphy would require that everything above one me- on the honesty of a private brick maker.... The inconsistent use ter to have been created afterwards. 25 As Wilson Jones argues in of dating cannot be readily explained by any single reason, but

the best reason to date bricks was to ensure that they had been a forthcoming article, this single stamp is likely to reflect the in-

exposed to weathering for several years. stallation of trim during the final stages of construction. Further investigation may result in more bricks dating from AD 123 being The largest bricks, bipedales, were often dated during the reign found in the dome, where relatively few bipedales have been re- of Hadrian (pls. 35 Β and 49Β). Bloch noted that brickstamps moved to be checked for brickstamps. from the numerous Hadrianic structures at Ostia had brickstamps Smith's article on Hadrian's Villa provides highly valu- with consular dates for 11 years of his reign: 120, 123-130, 134, able evidence for dating the Pantheon in relation to the vi11a. 26 and 138.22 New stamps were thus being regularly made and used He notes that 11 brickstamps occur both in the Pantheon and in throughout Hadrian's reign rather than outdated stamps continuing buildings at the Villa, the buildings of which were created almost to be used. entirely during Hadrian's reign. One of the stamps widely used Although stamps dating from 123 are encountered far more at the villa (number 315) was found in locations throughout the frequently than for any other year, this cannot be taken as evi- Pantheon. His summary of Block's evidence makes untenable dence that the tools made for that year continued to be used indef- Heilmeyer's assertion that most of the Pantheon was constructed initely. Considering that Hadrian was an architect, it is likely that earlier, and his conclusion is well supported: "I feel therefore an unusually large quantity of brick had been manufactured on his that the evidence of the brickstamps support the conventional dat- orders in anticipation of his return from his initial period of travel. ing of the Pantheon in the early years of Hadrian's reign rather Still greater caution must be used when considering evidence than an earlier dating."27 He noted that five stamps occur in both such as the thickness of bricks and mortar, color, and aggregates. the grottoni of the Pantheon and at the Villa; thus, there can be All of this type of evidence can be useful as, for example, dis- no question that the grottoni are primarily Hadrianic (with the tinguishing repairs when bricks cannot be removed to check for exception of the west wall, which is Severan and which he does brickstamps. Although there are many exceptions, Lanciani noted not mention). Hadrianic stamps were found in both stories of the 20

grottoni and in the arch in between the Pantheon and the Basilica same stamp with the possibility of an additional variant also 32 of Neptune. being represented). The building at Hadrian's Villa with features that most close- Combined total for Hadrian's Villa: 11 identical stamps. 33-36 ly resemble those of the Pantheon is the Serapaeum, which is part This simple comparison indicates that Hadrian's Villa pro- of the Canopus (pls. 190-191; Chapter 6B2). Domenico Faccenna duced about three times as many stamps used in the Pantheon as identified the 279 brickstamps found in the excavation of the Ca- were used in Trajan's Baths and Forum (including the Markets). nopus from 1950-1955 as having the following consular dates: It provides an example of how brickstamps can be compared more

189 from AD 123; 11 from AD 124; 17 from AD 125; 61 from objectively. Although the size of the samples is small, the results

AD 126; and 1 from AD 127. 28 This key complex of buildings was are consistent, and variant stamps were represented in proportion- thus constructed from about AD 126-129. It cannot have been ate quantities at each site. All that can be concluded on the basis constructed before 123 or long after 130. Mostly likely, it was of so small a sample is that the Pantheon has significantly more in begun as the Pantheon was being completed, but its dome could common with buildings of the Hadrianic Period than of the Traja- predate the Pantheon's dome. The building methods required to nic Period. Brickstamps alone do not suffice for any definite con- construct the Pantheon's dome must have been tested somewhere clusions about when the Pantheon was begun and completed, but on a smaller scale before being used on a building with an unprec- help greatly to narrow the range of possible dates. The evidence edented span. For this to be confirmed, all brickstamps from the of brickstamps will become increasingly valuable when all data dome of the Pantheon and from the dome of the Canopus would on where every type has been found is more readily available and need to be compared, and sufficient information is not now avail- when more objective comparisons can be more readily made us- able. Some additional samples may also need to be taken. It will ing a searchable database. There is no doubt that brickstamps can eventually be possible to use brickstamps to settle this question, be even more valuable than they are as evidence, but not until the but the level where every brick was found needs to be known to methods for their interpretation involve fewer assumptions. determine which dome was begun and completed first. In summary, since manpower and funding available to a Ro- During the Hadrianic period, stamps were more consistent- man emperor were almost unlimited, since the need for materials ly used than earlier or later and were used on most of the larg- had been anticipated, and since Hadrian was highly knowledge- est bricks (bipedales, which have stamps from 50 to 100 percent able about architecture, the period of construction is more likely of the time depending on the manufacturer). Only about 1 in 10 to have been shorter rather than longer than usual. It is unlikely smaller bricks were ordinarily stamped, and many of these do not that the Pantheon took longer to construct than much larger build- have the names of consuls and can only be dated approximately ings such as imperial baths, but it cannot have taken a great deal on the basis of their occurrence in buildings of known date. In less time. Crucial consideration were the thickness of walls and the case of the Pantheon, they do not provide better evidence than the weight of vaulting. Wall thickness determined how long con- numerous stamps with the names of the consuls, but they must struction would take, and thicker walls took longer to cure be- be taken into consideration. Although dated stamps cannot have cause all heat from the chemical reaction that was involved had been used earlier than the date on them, they can have been used to escape. The length of time required for one layer of concrete much later than when they were manufactured and so must also be to reach surncient strength for another layer to be added was interpreted with caution. They cannot, for example, be assumed crucial (Chapter 4G). Since this had long been known through to have been used immediately after manufacture for the construc- trial and error, the only delays in construction are likely to have tion of any building. been caused by design problems which arose as a building with Bloch usually summarized his findings numerically by brick- an unprecedented span was being constructed. Since there is also stamp for major Roman buildings, and his summary facilitates evidence of changes in design during construction, some further comparing the 43 types of stamps found in the Pantheon with delays are likely to have added to the total period of construction, finds for the same stamps in earlier and contemporary buildings: but the Pantheon cannot have taken longer to construct than far Trajan's Baths: 3 identical stamps, one of which is H αdri- larger buildings. anic.29 It is most likely that Bloch was correct that the Pantheon was Trajan's Markets: 2 identical stamps, one of which also oc- constructed from AD c. 118-126. It was in AD 118 that Hadrian

curs in Trajan's Baths and the other of which may occur in first reached Rome after becoming emperor, and it was around

another part of Trajan's Forum. 30 126 that the large number of brickstamps manufactured in 123 Trajan's Forum (Basilica Ulpia and Bibliotheca only): 2 iden- first began to be used at Ostia. His interpretation of the dates pro- tical stamps, one of which occurs in Trajan's Baths and Mar- vided by brickstamps is consistent with the historical and archi-

kets.31 tectural evidence. Although even dated brickstamps do not enable

Combined total for Trajan's Baths and Forum (including its buildings to be dated with precision, they are particularly useful

Markets): 3 identical stamps (2 of which are variants of the for establishing relative dates, and this will also be useful when 21 considering whether a particular building was designed earlier or scription, which was not copied either from Poggio or Palladio. 44 later than the Pantheon and consequently if it could have been a These three readings must have been taken from the inscription source for the Pantheon's design. itself, and increasing deterioration in the 15th, 16th, and 17th centuries suffices to account for minor differences. 45 Although the inscription is now badly eroded, parts are well preserved, and (IC) Confirming the Identity of the Three Pantheons judging by the earlier transcriptions, by the initial letters, by the spaces without letters, and by the sense of the inscription, there is The best evidence that the present building was referred to in good reason to believe that the word "PANTHEVM" was part of antiquity as the Pantheon are two specific references with descrip- the inscription. Although the transcriptions do not provide better tions: evidence to identify the building, better evidence is not needed. Dio Cassius wrote in c. 229 that the "Pantheion" has a "vault- Palladio did not hesitate to abbreviate or to expand abbrevia-

ed roof... [that] resembles the heavens." 31 tions. For the well preserved inscription on the frieze, he wrote, Ammianus Marcellinus wrote in c. 380: "the Pantheon [Pan- "Μ. AGRIPPA L. F. COS. III. FECIT," and he abbreviated TER- theum] like a rounded city-district, vaulted over in lo#y beau- TIUM as "III" (pl. 11). This translates as, "Marcus Agrippa, son ty "38 of Lucius, consul for the third time, built this."46 The implication These two references indicate that the name Pantheon was being is that the building was constructed in or somewhat later than 27 used from at least c. 200-c. 380 AD to refer to the existing build- BC, but it was probably begun in 25 BC. 47 The inscription on the ing, which by 200 was about 75 years old. frieze had bronze letters added in the 19th Century, but the bronze The Severan inscription on the Pantheon's portico can be dat- accurately follows the outlines of letters that show distinctly in ed to AD 202 or within a couple of decades of when Dio was writ- earlier photographs. ing about the Pantheon. 39 The name Pantheum has been repeatedly The existing building was believed to have been built by said to be part of this inscription, and it probably was when the Agrippa until Chedanne's discovery of Hadrianic brickstamps in inscription was transcribed in the 15th and 16th centuries. Now, 1892. Dii's description of AD c. 229 undoubtedly refers to the only the letters "PANT..." are visible (with the rest of the word present building, and even he was evidently misled by the inscrip- having been lost through spalling; figs. 94-95), but the amount of tion into thinking that this building was the Pantheon constructed space left where the letters have eroded suffices for the full name. by Agrippa even though he knew, but had forgotten, that it burned Multiple copies of this inscription differ so much that they were in AD 80, was rebuilt by Domitian, and burned again in AD 1 10 48 undoubtedly made independently of one another, and several Moreover, since the present building is fireproof, it is definitely made by reliable scholars include "PANTHEUM." The meaning not the building constructed by Agrippa and rebuilt by Domitian. of these different transcriptions is essentially the same, differing There is no definite evidence to tie the stone foundations only in minor wording. under the portico of the present Pantheon to either Agrippa or The most widely accepted version in the Corpus Inscriptio- Domitian. Considering, though, that construction in solid stone num Latinarium was based primarily on a copy by Poggio Brac- was characteristic of the Augustan Period and rare in the Domiti- ciolini made in the 15th Century. Letters that are not now visible anic Period, it is more likely that the stone foundations were built are in italics: by Agrippa. Considering that inscriptions on the portico refer to Agrippa and that they referred also to the Pantheon, the indirect IMP CAES L SEPTIMIVS SEVERVS PIVS PERTINAX evidence suffices to place all three buildings on the same site and ARABIC VS ADIABENICV S PARTHICVS PONTIF MAX to identify the pre-existing foundations as Augustan. The extent TRIB POTEST XIMP XI COS III P P PROCOS ET/ IMP of Domitian's work on the site is wholly unknown, and although CAES M AVRELIVS ANTONINVS PLUS FELIX AVG TRIG he may well have rebuilt Agrippa's building, he is unlikely to have POTESTAT V COS PROCOS PANTHEVM VETVSTATE CORRVPTVM CVM OMNΙ CVLTV RΕSΤΙΤVERVΝΤ.40 rebuilt its foundations. The reason why Hadrian put Agrippa's name on his Pan- Leaving out most titles, the inscription translates, "The Emperor theon or allowed it to remain on some reused parts of Agrip- L. Septimius Severus... and the Emperor M. Aurelius Antoninus pa's Pantheon is likely to have been in emulation of Augustus. [Caracalla]... restored with every care the Pantheon, repairing the The inscription by Augustus that was placed at the entrance of ravage of time."41 his mausoleum (his Res Gestae or list of accomplishments) in- Andrea Palladio's version of this inscription is essentially cluded the statement that he "restored [the Theatre of Pompey] the same. He wrote out "PANTHEVM" fully, but omitted "COR- at great expense without the inscription of my name." 49 By RVΤVΜ."42 It differs sufficiently in minor points that it was contrast, Domitian was criticized among other reasons for put- definitely not copied from Poggi ο's43 The inscription was often ting his name on buildings that he merely restored. Hadrian recorded later in very nearly the same way as in Desgodetz's tran- made it a regular practice not to add his name to any building 22

he built or restored with the exception of the Temple of Trajan public than the court. Law cases could be heard on the outside and Plοtina.58 of temples, but even this was exceptional. Augustus sometimes Gordon considered the inscription to Agrippa and concluded heard cases in the peristyle (that is, outside) the Temple of Her- that there was "nothing in the lettering to interfere with a Hadri- cules at Tivoli.54 Law cases were not heard inside temples," and anic date. However, he added that "no reliable criteria have yet the Pantheon does not have many of the basic features common been established for distinguishing [the lettering] of one century to temples. It was undoubtedly used for other purposes besides from another" earlier than the 4th Century ΑD.51 There seems to trials, but it cannot initially have been a temple. be no significant difference between the forms of the letters of the As a building type, a basilica has been defined as "a large inscription in honor of Agrippa and the inscription by Severs or public building whose principal function was to house law in the inscription by Hadrian on the bridge to his tomb. courts,"56 and it invariably seems to have served this function, but others as well. It was not exclusively a courthouse. Whether or not a case was being heard, basilicas were open to the public to (1D) Purpose of the Existing Pantheon discuss commercial transactions, politics, or any other subject. There is no evidence for commercial use in connection with Dio Cassius wrote that Hadrian "held court with the assis- the Pantheon, and it is unlikely that its few exedras were used tance of prominent men now in the palace [Palatine] or again in as offkces or shops, but the main space was undoubtedly used as the Form, the Pantheon, and in many other places, always on a an exchange and as a place for individuals to have discussions. platform, so that what was done was open to public inspection." 52 Similarly, the forecourt of the Pantheon was in between a form This indicates that the Pantheon was used as a courtroom and that and a bath, and its colonnade is likely to have served as a form, it was open to the public so that anyone who wished to could see but more as a place to meet or discuss business rather than as a that justice was being administered impartially. This is the sole place with shops. When voting ceased in the adjacent Saepta Ju- purpose the building is known to have served during the reign of lia, it was converted into an immense form and used primarily Hadrian. for commerce, a function it continued to serve after Hadrian re- It was not unusual for emperors to preside over major trials. built at least the part of it that is adjacent to the Pantheon.S 7 Trajan is known, for example, to have presided over the court of Dio's separate account of Agrippa's Pantheon of c. 25 BC the centumviri. Pliny the Younger, a lawyer as well as an author, and his account of the Pantheon as it existed in c. AD 229 were described a meeting of this court in the Basilica Julia in which 80 so conflated that what he wrote needs to be sorted out. About judges sat together to hear a case of exceptional importance. Or- the earlier building, he wrote that Agrippa had wanted to place a dinarily, this court was divided into sections with 20 jurors hear- statue of Augustus inside, but Augustus had refused to permit this, ing cases of lesser importance. Pliny wrote that on the occasion and, instead, Agrippa placed statues of Augustus and of himself of the larger trial, the Basilica Julia was barely sufficient for all outside the building. If the building had been planned or dedi- the people who wanted to attend.S 3 Such large attendance in some cated as a temple, Agrippa would certainly not have suggested cases indicated the need for still larger basilicas, and successively placing his own statue inside. Undoubtedly the interior contained the Basilica Ulpia, the Pantheon, and the Basilica Nova fulfilled statues of some, though by no means all, of the gods, but statues this need. of gods could be set up anywhere including, for example, an ath- Although court cases were not invariably held in basilicas, letic facility. providing a place for cases to be held was one of the primary If Agrippa's or Hadrian's Pantheon had housed statues of all purposes of basilicas as a building type, and it was not a primary the gods or even of the 12 Olympic gods, there would have been no purpose of any other building type. Basilicas were usually rectan- reason to doubt why it was called the Pantheon. It cannot have had gular such as the basilica Vitrvius designed for Fano (p1. 148 Α; either because Dio frankly admitted that he did not understand why Chapter 3Α), but for the Basilica Ulpia, Trajan added to each the building was referred to as the Pantheon: "It has this name, per- end of a rectangular space a pair of semicircular exedras with the haps because it received the images of many gods and among them diameter of the Pantheon, and together they had the same floor the statues of Mars and Venus; but my own opinion is that the name space as the Pantheon, but they were roofed with wood (pls. 175- is due to its round shape, like the sky." 58 He was writing about 176). Smaller law cases could have been held in exedras of the a century and a half after Agrippa's Pantheon had been destroyed, Pantheon or in the adjacent Basilica of Neptune, and Dio states and he confused Hadrian's dome with Agrippa's building. that Hadrian heard cases elsewhere besides the Pantheon. By around AD 229 when Dio wrote, the Pantheon then did Vitrvius noted that his arrangements for his basilica at Fano house "many," but not all gods or even the principal ones. It ensured that court cases would not interfered with business, and probably had statues of gods that Agrippa had undoubtedly hon- he implies that the commercial function was the primary one and ored: the deified and his divine ancestress Venus. the legal function secondary and more for the convenience of the Hadrian's Pantheon may have added a statue of Augustus on the 23 interior, but neither building was a temple to all the gods or all Size was not enough to create the impression of immensity. deified emperors. After being deified, both Julius and Augustus The surface of the dome had to be subdivided in some way that were given separate temples for their worship, and Hadrian was would enable its depth, shape, and scale could be readily per- given a separate temple when he was later deified. As Ziolkowski ceived. This was accomplished better than it had been before or pointed out, the inscription with Agrippa's name would be unique has been since through the use of a skillfully designed pattern of if it were for a temple in that it provides no indication which god coffers. or gods the building was supposedly built to honor. 59 Permanence was a consideration equally important with size. Pliny the Elder stated that Agrippa's Pantheon had a pedi- It had to be achieved structurally, and the building needed to be ment, and in this respect it resembled a temple, but Augustus had entirely fireproof. Concrete was chosen for both reasons—for its been allowed to place a pediment at the entrance of his house. structural soundness even in earthquakes and for being fireproof— Pediments had continually less religious significance, but pedi- as well as for enabling an unprecedented span to be achieved. mented porticoes continued to designate a temple. Similarly, the Since the Pantheon had previously burned twice, one of the depiction of sacrificial instruments on a building did not invari- principal concerns was to design a completely fireproof building ably indicate that it had a sacred purpose. to replace it. Area fires were taken for granted. Since the adjacent Further evidence that the existing building was constructed Saepta Julia had a wooden roof, the walls of the Pantheon needed as a basilica rather than as a temple is provided by the building to be firewalls like the wall behind the Forum of Augustus. The itself. It has the largest interior space created during Antiquity, need for fireproofing explains why the Pantheon had no windows and temples were not gathering spaces. It had a forecourt similar in its exterior walls, why brick-faced concrete was chosen as its to the one designed for the Basilica Ulpia rather than being placed principal material, why it was given unprecedented roof trusses of within a court like the Temple of Venus and Rome or projecting bronze, and why the shafts of its columns were granite. Windows into a court like the Temple of Mars Ultor. In its forecourt was facilitate the spread of fire; wooden roof trusses can be where a a triumphal arch, and a triumphal arch had been placed at the en- fire originates if, for example, a building is struck by lightening; trance to the Basilica Ulpia, but would have been inappropriate on and marble columns turn to lime with intense heat. Concrete axis with the front of a temple. Temples invariably had an altar in walls with a marble facing could have been seriously damaged by front of them placed near enough to be visible to a cult statue in- fires. Ideally, even the entablature and capitals should have been side, and no evidence of an altar has been found despite repeated of granite, but they could easily have been replaced if necessary, excavations in front of the Pantheon. Roman temples character- and the use of marble for details did not threaten the structure of istically were built on a podium whether they were rectangular the building. or circular, and when circular, they had a peristyle, and these are The greatest difficulty was to construct a dome of unprece- two additional features the Pantheon does not have. With the ex- dented size as part of a free-standing building. Even most smaller ception of a pedimented portico, the evidence of typology corre- domes had previously been constructed as integral parts of other sponds to the only documented use of the building, and evidence buildings and used the walls of adjacent rooms to buttress them. will be presented that the pediment was added to a previously un- There were some precedents for other building types that used pedimented portico (Chapter 13C4). buttresses constructed as parts of walls, but no precedents are def- initely known to have existed for the steprings that successively enable the space that needed to be spanned to be minimized. (1E) Main Problems to Be Solved by the Architect

The principal challenge for the architect was to design the (1F) The Client and the Architect largest domed space ever created. A major part of the dome's im- pressiveness was intended to be its size. Hadrian had personally There is no record of who designed the Pantheon, but Hadri- designed the largest temple and built the largest tomb ever con- an may well have been both client and architect. He was an archi- structed in Rome, and by doing so, he was following the example tect, and he designed the Temple of Venus and Rome, which was of earlier emperors who had successively created the largest cir- dedicated on 21 April 128 (pls. 202-203). 60 In addition to being cus (Julius), the largest theatre (Pompey), the largest amphitheatre a highly effective emperor, he had previously served as a general (Vespasian), and the largest forum (Trajan). These Romans hoped and provincial governor. He had first-hand experience in design, to surpass their predecessors and their successors, and all of them in construction, and in the organization of large-scale operations. succeeded. In terms of scale, Frontinus pointed out that the aque- There is good evidence that before becoming emperor, Hadri- ducts of Rome surpassed the pyramids in the effort required and an had designed innovative domes. When he commented on a de- that they were far more useful. The Romans customarily built on sign by Apollodorus, the architect of Trajan's Forum and Baths, the largest possible scale. he was told, `Be off and draw gourds. You don't understand any