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Home , Alexandria, Hippodamus of Miletus, Polis

The astronomical orientation of the urban plan of

Luisa Ferro and Giulio Magli Faculty of Civil Architecture, Politecnico di Milano, Italy

Luisa Ferro Faculty of Civil Architecture Politecnico di Milano Italy [email protected] +39 02 23995618

Giulio Magli Faculty of Civil Architecture Politecnico di Milano Italy [email protected] +39 02 23994505 1. Introduction

According to ancient sources, founded Alexandria in 331 BC (Bagnall 1979). The was planned in compliance with the “orthogonal grid” principles which are usually referred to as “Hippodamean”, but actually appear in the planning of Greek colonies quite before the life of Hippodamus of (Castagnoli 1971, Shipley 2005). The orthogonal grid of the ancient city can still be perceived, and forms the basis for an ongoing project of reassessment of antiquities in Alexandria into a coherent architectural scheme of fruition (Ferro and Pallini 2008, Torricelli 2010a, 2010b). The town was wholly designed from the very beginning in all its details, with a relatively huge perimeter, and divided into five areas named after the first five letters of the . The original matrix route was conceived on the basis of a main longitudinal axis, later called Canopic Road; the most important transverse axis was a dyke (Eptastadion) connecting the mainland with the isle of Pharos. The Canopic Road was conceived as an “extended centre”, a wide, longitudinal open space, with the main buildings distributed along it, avoiding the idea of a “central point” as the focus of the Urban Plan. The first who put in evidence such a “longitudinal” character in the original project was 19th century astronomer Mahmud Bey Al-Falaki (1861). Later in time excavations along the modern road showed that the Canopic Road was actually deeply etched in the rock subsoil (Breccia 1914). The main “longitudinal” urban matrix remained a constant in the successive phases of development of the city up to modern times. In Roman times, however, the transverse axis was extended in order to improve circulation and to form a cross-like main axes urban plan, as referred by (Caruso 1993, Ferro 2010). In spite of what is emphatically reported by in his Life of Alexander (26, 2-3), the site where the newly founded town was built did not have special characteristics of suitability. In particular, the city was planned in a strip enclosed between the sea to the north and west, the marshy lands of the mouth of the to the east, and Mareotis Lake to the south, in contrast with the criteria stated by Alexander’s tutor, , in his (Bernand 1995). A series of preliminary works was required in order to construct the city in the desired place. Alexander’s Romance reports about the existence of 12 channels which had to be dried in order to cover them with streets, and excavations have in fact shown the existence of at least 3 of such channels. All in all, we are led to consider the foundation of Alexandria as a truly symbolic act, inspired by “religious” criteria and aiming at the celebration of Alexander’s power and divine nature (Ross Taylor 1927). Such a foundation probably was in compliance with the – already old – ritual: indeed the founders visited an oracle before starting their enterprise. Typically, it was the oracle at . Alexander, however, visited the most important oracle in , the Ammon oracle at Siwa, and this probably occurred just before the foundation of the town (Bradford Welles 1962). The founder played the role of ancestor for the town as a whole, and he was to be buried “in the center of the city” (Detienne 1998). Examples of sepulchres (or at least cenotaphs) of founders are known from both the Greek (e.g. ) and the Roman world (Lavinium) (Rykwert 1999). The burial of Alexander – if it existed - has not yet been found though. An interesting fact about the planning of Alexandria (to be thoroughly discussed later on) is that the orthogonal grid seems to be not conformal to the characteristics of the landscape: the strip enclosed between the sea and the marshy lands of the Canopus mouth of the Nile. On the other end, it has been repeatedly suggested that several Roman towns whose orientation does not conform to peculiar features of the landscape were oriented in accordance with astronomical, rather than utilitarian, criteria. This fact has been recently investigated in a systematic way in the case of the Roman towns in Italy (Magli 2008). The present paper aims at investigating the same issue in the case of the orientation of Alexandria.

2.The astronomical orientation of the urban plan of Alexandria

As mentioned above, the rectangular grid of Alexandria was based on a main “east-west” road, the so called Canopic road which crossed the city leading to the Canopic mouth of the Nile and the Canopus (today Abukir) bay. At the opposite ends of the street two main gates were located; at least since the work of (early second century AD) the east and west gates were called Gate of the Sun and Gate of the Moon respectively (Haas 1997). The Canopic road bears an azimuth of 65°15’ ± 30’. The horizon to the east extends towards the Abukir bay and was therefore flat in ancient times; the same holds to the west. Eventually, the unique favorable point for the surveyors of the newly founded town was the “hill” of the , located to the south-west of the town, but even in this case the elevation is negligible (some 15 meters) so that the horizon on the sea can be considered as flat on both sides. In 331 BC, the azimuth of the rising sun at the summer solstice (occurring on June 28 ) was 62° 20’ (today it is slightly displaced due to the variation in the obliquity of the Ecliptic). Therefore, it can of course be said that the orientation of Alexandria axis at 65° 15’ is “solar” in that the sun was (and is) rising along its direction twice a year. The sun was rising with this azimuth on July 24 (and on the symmetric date with respect to the summer solstice, June 2). The range - one degree wide - centered on this value was achieved in a period of a few days before and after this date, respectively. It is the aim of the present paper to defend the idea that such an astronomical orientation was deliberate. First of all, one could hypothesize a very rough solstitial alignment. However, an error of some 3 degrees looks quite exaggerate, both for the Egyptian and for the Greek standards of the period (Magli 2009). We propose here a quite different, striking possibility, namely that the city was oriented to the rising sun on the day of the birth of Alexander the Great. Alexander the Great was born on July 20, 356 BC. In the 4th century BC the sun was rising on July 20 at an azimuth 64° 30’, only 45’ less than our best estimate for the azimuth of the Canopic Road. The Julian date of birth of Alexander, however, has nothing to do with the calendar in use in that earlier period, and therefore our proposal requires a careful discussion. It is most probable that the calendar used by the planners of Alexandria was not the Egyptian solar (“civil”) calendar. (Running 365 days per year, this calendar lost around 6 days in relation to the sun cycle between 356 and 331 BC). It was, rather, the luni-solar Greek calendar. Actually, according to ancient sources such as Plutarch, Alexander was born on the sixth day of Hecatombaeon, the first month of the year. New year’s day was the day of the first new moon after the summer solstice, and, in 356 BC, this occurred on July 14, leading to July 20 for Alexander’s birth. Due to the length of the synodic month (about 29.53 days) however, the date of the new moon after the summer solstice varies from year to year, so that Hecatombaeon 6 wanders trough different solar dates as well. In other words, the date of birth of Alexander is not a fixed day of any solar calendar. It is, however, also true that Greek astronomers were perfectly able to trace the date of the new moon back in time. Indeed the Metonic cycle (stating that 19 tropical years are needed to complete 235 synodic months) was known to them since the 5th century. 3. Discussion

When a deliberate astronomical alignment is proposed, it is of course fundamental to investigate the possibility of a mere coincidence. If the sample under exam is wide enough, a statistical analysis can be applied to evaluate the probability of casual alignments (Ruggles 2005). A similar analysis has been recently carried out by one of us in the case of Roman towns in Italy (Magli 2008). Unfortunately, no such analysis is available for Greek and/or Hellenistic towns. In addition, Alexandria is by all means unique in that its foundation is not the result of a colonization process. To investigate this issue we can, however, at least concentrate on a related point: was the orientation of the rectangular grid dictated by topographical reasons? The answer appears to be in the negative: the orientation of the grid was not due to utilitarian or functional reasons. A quite natural choice indeed would have been to trace the longitudinal axis parallel to the shoreline, which has a mean azimuth around 49°. Choosing such an azimuth would allow the planning of a main road along the seashore. To convince ourselves we can refer to the (slightly later) rules codified by the Romanagrimensores. When they planned centuriations, they could act secundum coelum (that is, using astronomical orientation) or secundum naturam. This second procedure was based on the adaptation of the grid to the physical characteristics of the terrain. Usually, near the sea, this was the exceedingly preferred choice, and implied that one direction of the grid was orthogonal as much as possible to the shoreline, so that the alternate one was essentially parallel to it. A clear example is the centuriation of Ager Lunensis (today’s Luni, Ligury) carried out in 177 BC (Smith et al. 1986). An independent confirmation comes precisely from the work of Roman architects in Alexandria. When they sat about to construct the Caesareum (probably founded by in honour of and later dedicated to ) they apparently felt the “failed” orthogonality of the grid to the main shoreline direction as a disturbing fact. Planning the temple in conformity to the existing grid did not give a satisfactory view to the front of the and therefore to the people arriving from the sea. The temple is now lost but its position has been reconstructed on the basis of the which were still standing in Alexandria in the 19 century, and – at least according to McKenzie (2008) - the front formed an angle of (roughly) 15° (i.e. 64-49) with the pre-existing grid. A similar analysis applies to the Imperial . In this case as well, the building has not survived, but the Arab walls have been traced along its foundation, and again they appear to break the grid and to adapt to lines parallel to the shoreline. A final hint to a likely deliberate orientation of the grid to Alexander’s birth comes from the fact that this day was, together with the foundation of the city (Tybi 25, which fell on April 7 in 33I BC) the most important festivity of the town, celebrating Alexander as a living God. As any festivity fixed according to the moon (e.g think of Christian Easter) the date varied from year to year. However, due to the waving of the lunar calendars and to differences between different local calendars, the probably elaborated astronomical methods to act as warnings for relevant festivities, such as observing heliacal rising of specific constellations (Hannah 2005, 2009; Salt and Boutsikas 2005). Was the Alexandria alignment operational in this sense? The “King’s Star” Regulus (alpha-Leonis) was at that time rising at the very same azimuth (65° 20’ at altitude of one degree, appropriate for the visibility of a first magnitude star) and had heliacal rising very near to July 20 (the precise date of Heliacal rising of a star depends on many factors and cannot be defined with high precision, see Schaefer 1986). Furthermore, the alignment to the rising sun in the companion solar date might have been used as a solstitial marker – and therefore as a “correct new moon warning” - occurring a number of days (26) close to a lunar month before the summer solstice. Acknowledgments

The present work arises within a vast research project devoted to the enhancement of the Archaeological Areas of Alexandria, co-coordinated by Angelo Torricelli whose constant help and encouragement is gratefully acknowledged. The project includes a collaboration with the University of Torino, the Alexandria & Mediterranean Research Center, the Department of Architecture of Menofeya University and the Italian Archaeological Mission at Alexandria coordinated by Paolo Gallo. The current project mission entitled “Kosa Pasha Fort, Abuqir” is operating under an International Protocol of scientific collaboration with the Supreme Council ofAntiquities (SCA) of Egypt. Architect Elena Ciapparelli, who has worked on images, and students Marina Bianconi and Valentina Sala are also gratefully acknowledged.

Captions

FIG 1 Alexandria, the original town plan superimposed on the reconstruction by Mahmoud-Bay (1866) (Courtesy of CEAlex Archives J-Y. Empereur).

FIG 2 Alexandria, reconstruction scheme of the original town plan. 1) Canopic road 2) Heptastadion 3) Serapeum 4) Imperial palace 5) Isle of Pharos (@ Luisa Ferro)

FIG 3 The original town plan superimposed on the plan of the Alexandria area from the city to Canopus/Abukir (from Description de L’Egypte (1803); courtesy of CEAlex Archives J-Y. Empereur).

FIG 4 A photograph of the early 19th century showing the Canopic road, looking west (courtesy C. Pallini).

FIG 5 The position of the Caesareum in relation with the pre-existing grid and the sea 1

2 3

4 5 References

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