The Characteristics of Star Vaults in Seljuk Anatolia A.T. Yavuz Middle

The characteristics of star vaults in Seljuk

Anatolia

A.T. Yavuz

Middle East Technical University, Faculty of

Architecture, Master Program in Conservation,

ABSTRACT

Both in the medieval gothic world as well as in the Near East there are vaults which display various star shapes in their plans.

Several of these plans are very similar, however, the sections, the geometric form they are part of, the existence or the non-existence of ribs produce a large variety in different parts of the medieval world. The intention of this paper is to introduce the characteristics of the Seljuk Period star vaults in Turkey and compare them with other star vaults in other parts of the world.

INTRODUCTION

Architectural historians are well aware that many medieval and later monuments have vaults which include a star form in their plans and they are called "star-vaults". This paper will limit itself only with those vaults where the stars are not mere decoration but the lines that contribute to the starform are integral parts of the vaults, that is the vault could not be defined or just exist without their presence. In such vaults the lines of the star may coincide with the ribs, they may correspond to the groins where various facets meet, they may also form the groin where two different vaults with different profiles or different volumetric forms meet. In some cases they may be further emphasized by coloring the lines or by the contrast between the cut stone ribs and the plastered rubble stone webs between them.

Anatolian Seljuk Star Vaults

Anatolian star vaults do not altogether form a different type of vault from the types already known. They are all a derivative of the cross vault which constitutes 20% of all types of vaults and domes in Anatolian Seljuk architecture. They display

166 Structural Repair and Maintenance of Historical Buildings

such characteristics of the cross vault as the profile at the four sides, the groin lines where the two barrel vaults meet, the typical section of the cross vault which is a straight horizontal line because the intersecting barrel vaults are parts of cylinders. The form of the star is the result of facets folding in and out and which start at the corners.

There are altogether twenty-two examples that have survived to our day from the Xllth and the XHIth Centuries. Nine of them are intact or with little damage, six of them are so badly damaged that they could not be measured, and seven of them do not cover a space or a bay by themselves but are part of a larger combined or composite superstructure. All except the one in the Han near Igdir, Kars [R.H.Unal (3)] have been measured and studied in detail, which are fifteen altogether [A.T.Yavuz (1)]. These vaults have been studied between the years 1965- 1982. Their measured surveys in 1/20 scale include a plan, a plan of the coursing of the material, at least one section, and the geometric set-up of the vault [A.T.Yavuz (1,2)].

Anatolian Seljuk star vaults are of the faceted kind and they can be a classified according to the number of the facets which are created by the lines that may be interpreted as the multiplication of the groin at each arm of the vault. A secondary criteria for the classification is the geometric form of the "center" of the vault, to the corners of which the lines join. Some corners of the centers accommodate two lines from two arms whereas some others have only one line meeting the corner. This depends on the relation of the corner to the springing point of the lines at each arm. Usually the corners on the midline of the sides accommodate two lines. The differentiation from the cross vault starts with 2 lines, instead of the single groin line. The extant Anatolian Seljuk star vaults vary between those with 2 lines-3 facets to these with 7 lines-8 facets, but the majority of them have 3 lines-4 facets. Generally the lines between the facets are odd in number rather than even. This contributes to the continued existence of the groin line emphasizing their basic relationship with the cross vault as well as forming a symmetry axis on each arm of the vault. Another shared feature is the coursing of the material both in stone and brick. The courses start perpendicular to the sides, as is common in cross vaults but they fold at the facets following the outline of the center, parallel to it. This type of coursing creates concentric replicas of the geometric form of the center, like ripples in water, emphasizing its form.

Structural Repair and Maintenance of Historical Buildings 167

Examples

The only extant star vault with 2 lines-3 facets is located on the east end of the north riwaq in the Keykavus Daru§§ifasi

(Hospital) (AD 1217-20) in Sivas. The central and the north parts of the vault have crollen therefore the form of the center cannot be determined even though the 2 lines and 3 facets of the arms are clearly visible. The number of lines from four arms require four corners to join. A square center with its corners pointing to the midpoints of the sides seems to be the right geometric solution and this is the form of the centers at similar star vaults in the Ye§il Cami and Medrese in Bursa, from the Early Ottoman Period (Photo 1). In vaults with 2 lines-3 facets, because there are even number of lines the groin lines of the vault have disappeared instead the facets which determine the four arms of the star are more emphasized.

The majority of the star vaults have 3 lines-4 facets.

There are seven intact or partially crollen, four badly ruined or completely crollen vaults of this type covering individual spaces or bays. There are seven others, used completely or partially, as parts of other combined or composite super- structures, adding up to eighteen altogether (the latter group will not be part of this paper except for comparison). These vaults have similar features but no two are exactly alike. All of them, except one, have octagonal centers. The octagon is so located that its corners are on the bisectors of the sides and the diagonals of the vault. The three lines that start from each corner of the vault join the corners of the octagon nearest to them. Neither size of the octagonal center, its geometric relationship with the vault, nor its treatment as a straight, recessed or articulated panel effect this basic relationship.

The star vault with the unusual center covers the fifth bay from the West, in the south riwaq in Sivas Keykavus Daru§§ifasi (N.4.20m/S.4.24m/E.4.32mAV.4.26m) (Figure 1,2). The brick vault has a two near-centered-recessed shouldered profile. There are four equilateral triangles, one on each side, starting with its base on it. The sides of the triangles extend towards the center forming a four-armed star, each arm of which is equal to the generating triangle. The central one of the 3 lines meets the corner where the tips of the two reverse triangles meet whereas the outer two lines join the inner corners of the star. It is not possible to detect if the generation of triangles and stars continues further or if there is only a plain square at the center because the central part of the vault is partially crollen, partially plastered. But it is clearly visible that the coursing of the bricks follow the

168 Structural Repair and Maintenance of Historical Buildings

outline of the star and the triangles, whereas it is parallel to the side of the vault inside the exterior triangles.

Another brick example is over the entrance eyvan in Sivas

Gok Medrese (A.D.I 271) (Photo 2). The star covers the square area at the center of the rectangular space (N.6.38m/S.6.38m/E. 3.89m/W.3.80m) and the intersecting barrel vault extends further in the north-south direction to cover the areas at the ends. The basic cross vault has a two centered - pointed profile. The octagonal center which is equal to half of the width in size is treated as two concentric rings. The outer one is 0.96m in diameter and is recessed 0.06m whereas the inner one, 0.96m in diameter, is in the form of a lobed projection hanging from the center. The vault is completely plastered and whitewashed now but there is the possibility of the use of glazed bricks or colored tiles, especially at the hanging center.

The 3 lines-4 facets star vault over the second bay from the East of the fourth horizontal aisle from the South in Divrigi

Ulu Camisi (Great Mosque) (AD 1228-29) also has a rectangular plan but this time the plan is reduced to a square by a 0.96m wide arch on each end of the long sides (N.4.53m/S. 4.50m/E.4.66m/W.4.62m). The vault has a depressed two-centered- pointed profile. The octagonal center is rather a large one, occupying three fifths of the width and consists of two eight pointed stars, one inscribed within the other. The outer, larger star, the arms of which is painted in red is recessed about 0.04m, whereas the smaller inner one is protruding about 0.15m in section (Figure 3). Each star is formed by specially shaped stones to form and emphasize the geometry of the stars. Some irregularities in the coursing as well as the quality of the mortar indicate to a repair done using the original stones of the vault.

The tiirbe (mausoleum) in Karatay Han (AD 1240-41) on the Kayseri-Sivas road is in the form of a deep eyvan (N.S.3.52m /E.W.5.22m). The square planned star vault takes place at the rear of it, over the sarcophagus and the front part is covered by the extension of the intersecting barrel vault (Figure 4,5). The section of the vault has a two centered pointed profile. The octagonal center which is equal to half of the span is treated as two eight pointed stars in two stages, like the one in Divrigi Ulu Camisi. In section the stones of the outer star are recessed by 0.05m and the inner star is treated as a pyramid, receding another 0.36m at its tip. The whole surface of the center is painted, the arms of both stars in white and the rest in red. There are remains of plaster and whitewash on the cut stone as well, which indicate to

Structural Repair and Maintenance of Historical Buildings 169

a later intervention.

The star vault (N.4.85m/S.4.87m/E.4.89m/W.4.90m) over the east eyvan of Hatuniye Medresesi (AD 1250-1270) in Erzurum has a center with a diameter equal to half of the span, like the

Karatay Han example. Here, however, the inside of the octagon is treated in a different way. At the periphery there is a ring a lozenges and in it a recessed, eight printed star (Photo 3, Figure 6,7) all parts of the center are faceted, recessed or embossed within a depth of 0.15m. A similar geometric set up is also seen in the central star vault of the composite vault covering the royal loggia [A.T.Yavuz (3)] in Divrigi Ulu Camisi (Figure 13). It has the same two-centered pointed profile observed in most vaults of the monument.

The fountain eyvan in Alara Han (AD 1232) near Alanya has a vault (N,S,E,W 3.90m) which is somewhat different than the other 3 lines-4 facets star vaults. It has a rather small octagonal center which occupies only one third of the span. The geometry inside the octagon does not generate from that of the vault (Figure 8). The outer ring is formed by arms of two eight pointed stars interweaving in two different planes. An inner ring of lozenges limits the arms of the stars at their lower ends. In the section these two rings recede 0.17m in two steps. Unlike the centers of other vaults which are composed of specially shaped cut stones, the center of the Alara Han vault is one big monolith with everything carved on it. At the present there is an octagonal cavity in the middle of the stone, giving the impression of an oculus, however a careful examination of the cavity shows that there was another piece of stone inserted in it which is now missing. This stone should have been decorated in a stalactite form and should have been highly protruding in section to necessitate its being shaped from another piece of stone. The section of the vault is two-centered pointed.

The entrance eyvan of the Sultan Han (AD 1232-1236) on the Kayseri-Sivas road is rectangular in plan (N.S.4.52m/E.W.6.12m). The star vault is located at the center and the intersecting barrel vault on the N-S axis extends over the rest of the rectangle. The vault has a two-centered pointed profile. The center of this vault seems to be the simplest of all with two plane, concentric octagons without any decoration (Figure 9). However A.Gabriel (8) mentions it to a partially crollen half- dome and the drawings done before 1930 show it. Apparently the vault has been reconstructed in the restorations done after 1962 and the half dome was replaced by the present center [A.Tukel (Yavuz) (4)].

170 Structural Repair and Maintenance of Historical Buildings

All the vaults of the north riwaq of Mar din Ulu Camisi

(c. end of the Xllth C.) have crollen and have been replaced by simple cross vaults. The extant springing stones, however reveal that four vaults, two on each side of the middle one were star vaults with 3 lines-4 facets.

There is no example of a 4 lines-5 facets star vault in Seljuk Anatolia neither in single nor combined form. The only example, the composite half-axis shifting star vault over the south eyvan of Turan Melik Darii§§ifasi (AD 1228-29) in Divrigi is not discussed here because it is belongs to a different group of vaults and it is a composite example.

There are only two 5 lines-6 facets star vaults covering a single space or bay and two others as parts of other super- structures. Three of these form a group in themselves in relation to the geometric form of the center they utilize. Of this group the single example covers the entrance of a Han near Igdir, Kars (end of the XHIth C. AD), which could not be visited by the author but published by R.H.Unal [R.H.Unal (5)] (Photo 4). The two others are both in Divrigi Ulu Camisi. One of them is part of a combined superstructure covering the fourth bay from the East in the southern horizontal aisle (Photo 5). The other composite example is over the second bay from the East in the second horizontal aisle from the South (Photo 6). In all three, although those are variations in the surface decoration of the arms and the area in the middle, one geometric solution is used for the center. The center has a cross plan where each arm ends with a triangle. Of the 5 lines starting each corner, the central one (the groin) meets the corner between the arms, the next ones on each side meet the corners where the straight and the triangular parts of the arms join and the outermost ones meet the tips of the triangles. The wide arms of the centers also effect the profile of the vaults as well; they all have two-near centered- shouldered profiles.

The different 5 lines-6 facets star vault is over the first floor space above the entrance in the Turan Melik Darii§§ifasi in Divrigi. It has a two-centered pointed profile. The rectangular space is turned into an almost square squarish (N.4.15m/S.4.11m /E.4.84m/W.4.84m) by means of a 0.96m arch on each side. The center of the vault is composed of several pieces connected to each other (Figure 10,11). At the middle there is a hexagon, in size equal to half of the span. Two of its sides are parallel to the north and south sides of the vault. There is a shallow cupola

inside the hexagon, constructed with its stones coursed in a spiral. Lozenges are attached to the hexagon as secondary centers. The double lozenges on the north and south sides are connected along their sides whereas the single lozenges on the east and west sides are joined from their tips. The opposite tips of all lozenges touch the sides of the vault. This vault is symmetrical on the north-south axis only, as is obvious from the arrangement of the centers, their form, number and connections. Of the 5 lines, the ones at the center meet the corners of the hexagon where no lozenges are attached. The next ones on each side meet the corners where the lozenges meet the hexagon, and the outermost ones meet the free corners of the lozenges. The facets of this vault are not symmetrically equal on the two sides of the groin because it is symmetrical on a single axis only and because it is not exactly a square.

The star vault of the main eyvan of Turan Melik Darii§§ifasi is the only extant star vault with 6 lines-7 facets. The eyvan is a squarish rectangle in plan

(N.8.78m/S.8.76m/E.7.43mAV.7.44 m). The star vault is placed over the square area at the rear of the eyvan and a band of 1.22m near the mouth of the eyvan is covered by the extension of the intersecting barrel vault, as though it were the eyvan arch (Figure 12). The profile of the vault is two centered pointed. In this vault the center is composed of several geometric forms next to each other. The irregular octagon in the middle is so placed that its four sides are parallel to the sides of the vault. These four sides extend in four directions with rectangular arms that end with triangles. Of the 6 lines that start from the corners the two at the center meet the corners where the arms meet the octagon, the next ones meet the corners where the arms and the triangles join and the outermost ones meet the tips of the triangles. The groin line is lost because the lines are odd in number. The octagon in the middle is a 0.08m recessed plane panel, its stones are coursed in a double spiral. The stones of the cross arms are carved with geometric interlace. The central facet is carved in a concave curve and it ends as an oyster at its wider end near the octagonal center. The visible irregularity of the center stones as well as the relationship of the decoration to the geometry of the stone pieces imply that these stones were not prepared for this specific location but were used here with a sense of economy which is apparent in other superstructural elements of both the Mosque and the Hospital in Divrigi.

The star vault with the most articulated arms was covering the central bay in the north riwaq of the Ulu Cami in Mardin,

in between other star vaults with 3 lines-4 facets. This vault has crollen and a simple cross vault has been constructed over its remains. The traces on the springing stones show that each arm was divided into 8 facets by 7 lines.

Historical Perspective

Seljuk Anatolian star vaults with facets and no ribs have no parallels in the gothic world where the star vaults utilize the rib and web construction. However, a special type of vault which J.H.Acland (10) calls "prismatic cellular vaults", "folded-fan" shows some interesting similarities. These vaults appear in Spain in stone, and in Bavaria, Saxony and the nearby regions in brick. The earliest example is in Santo Domingo, Valencia (1437) whereas most of the vaults of the latter area are from the second half of the XVth Century and the XVIth Century. They look more like a combination of star vaults and the so called "Turkish triangles" which are used as transition elements. The surface treatment of these vaults is more prismatic and much subdivided with facets covering the whole surface of the vault, not only the arms as the case is in the XHIth Century Anatolian examples. J.H.Acland (10) considers a near eastern influence after the XlVth Century through clerics and travelers.

A survey of the near eastern monuments between the Xlth- XlVth centuries gives interesting results [A.Yavuz (1)]. The Great Seljuk vaults in Iran are not star vaults of the Anatolian

Seljuk type. First hand studies by the author in Isfahan Mescidi Jami have shown that they are either pendentive domes, domical vaults or cloister vaults with a star decoration created by coursing or they are cloister vaults with interlacing ribs which result in star plans. No star vaults and very few cross vaults are used in the Byzantine architecture of Turkey. A rather profound research on the published sources in Armenian architecture has resulted in one star vault the date of which was certain. It is in the 1339 dated S.Astvatsatsin church built on the exterior wall of the Noravank Monastery [P.Cuneo (7)]. It is a 3 lines-4 facets star vault. An earlier example which is said to exist in Kauligia Monastery [L.Hautecoeur, G.Wiet (8)] could not be traced. Syria and Palestine are the regions which produced star vaults more similar to the Anatolian Seljuk examples the earliest of which covers the frigidarium of Gazi Hamami in Aleppo that is constructed before 1215 [J.Sauvaget (10)]. The majority of the dated ones belong to the XlVth century. There is no star vault earlier than this date in the Mamluk Egypt either.

Structural Repair and Maintenance of Historical Buildings 173

Although the earliest example (the riwaq vaults in the probably Xllth century dated Ulu Cami in Mardin) is in southern Anatolia the abundance of the star vaults in number, their spreading all over Anatolia and the use of brick as well as stone all indicate to a unique development in Anatolia with some parallels in Syria. In the XIYth to the XVIth centuries the star vault spread, flourished and became more elaborate in design in Syria, Palestine and Egypt whereas its use became very insignificant in Ottoman architecture.

Evaluation

Star vaults are preferred to be used over individual spaces at special locations, except in buildings composed of bays like Divrigi Ulu Camisi and the north riwaq of Mardin Ulu Camisi. These can as well be can interpreted as special locations of an extended nature. The choice of special locations is not true for star vaults only but for all types of decorated superstructural elements, to put it the other way around decorated vaults and domes are preferably used over special locations. But since star vaults constitute the majority of the decorated vaults, the relationships of the special location and the star vault is more significant.

These special locations are not rooms defined by four walls and entered by a door. They are spaces or units which are easily perceivable from many viewpoints and detectable from different angles once inside the building. Among the star vaults discussed only one is over a closed entrance space with two doors, all the rest are over more open and more easily accessible spaces. The majority of them cover eyvans which are defined by three walls on the sides and the rear whereas they are completely open at the front side. They open directly to a courtyard or indirectly by means of a riwaq. These eyvans are main or side eyvans of medreses which may be used as classrooms or prayer areas, they may be a fountain or a ttirbe eyvan, as in the rare case of Karatay Han.

The material used in the star vaults is either cut stone or brick. The need for the exact implementation of the geometry did not allow for rubble stone to be used. The choice of material is not done on the basis of individual structural elements but on the basis of building itself in general. Stone is always the preferred material although brick is not uncommon. Brick vaults are part of brick structures and there are many monuments where combined

174 Structural Repair and Maintenance of Historical Buildings

use of materials is observed, especially in the superstructure.

The relationship of material and profile is less apparent in star vaults because the relationship of geometry is more decisive in the choice of the profile. If the geometry, in relation to the center, necessitates a profile different than the most preferred two- centered pointed profile, it is usually a shouldered profile. The volumetric form utilized for all the barrel, cross or star, and cloister vaults are part of one and more cylinders or combinations with them, depending on the profile. The bases of the cylinders used are on a horizontal plane therefore all sections display the basic horizontal section line parallel to the ground. Neither cones nor hemispheres are used in any of the above listed vaults of the Anatolian Seljuk Period.

The size of the individual centers are usually half of the span or more, that of Alara Han is the smallest with a size equal to one third of the span. The larger the center the more is the area to be decorated and the wider is the spacing between the facets which makes them more pronounced. The centers spread to the surface of the vault in chains when the vault is more faceted. The increase in the number of facets changes the form of the center from square, to pentagon, to hexagon, to octagon, to square with cross arms ending with triangles, to octagon with cross arms ending with triangles, and to a basic hexagon or octagon with one or chains of lozenges added, enough to provide the necessary corners. The alternative of increasing the corners of the central polygon is not preferred because each facet needs a certain width to be seen, this means that the points that the lines join must spread towards the sides of the vault to provide this width when the number of facets multiply.

The geometry of the star vaults generates from the plan dimensions of the vaults. The form, size, relationship of various parts of the center as well as their decoration all may generate from the same geometry. The geometric tools used can be the diminishing square, concentric squares, grids of squares or triangles, interlacing lines, and a combination of these [A.Yavuz (2,4)]. The geometric tools used apply to other decorated vaults as well and only the compass is enough to construct the geometry of the plan as well as that of the section.

The articulation of the centers and of the facets, already discussed in plan, section, and the coursing of the materials, are clearly visible on the intrados of the vaults. However it is not possible to determine the section of the extrados because it is not

Structural Repair and Maintenance of Historical Buildings 175

accessible. The star vault in Alar a Han is a rare example where the extrados can be studied. Here it can be easily observed that the faceted section does not repeat itself at the extrados. It reveals the section of a regular cross vault. The reduction in the section due to faceting does not effect the carrying capacity of the vault because the thrust lines of the vault remain within the thickness of the vault which is 35-50m. However some more investigation of the extrados of the vaults is necessary to be able to generalize.

The use of stars in the superstructure is not limited with star vaults. A large group of cross vaults have four-pointed star centers without the facets, many domes have stars produced by the coursing of the bricks or revetted by tiles having interlacing stars. The abundant use of the star in other kinds of decoration as well only leads us to the iconographic evaluation of the star form. However what makes the star vaults very special is the unusual integration of the star with the cross vault to produce a very unique type of vault although not different in structural behavior than the original cross vault.

176 Structural Repair and Maintenance of Historical Buildings

References:

1. Yavuz, A.T., Selguklu Devri Anadolu Mimarisinde Tonoz ve Kemer, Ankara, 1983, pp.34-58, 161-169, 290-324, 454-465.

2. Yavuz, A.T., "The Geometric Patterns of Anatolian Decorated Vaults" in Fifth International Congress of Turkish Art, ed. Feher, G., Akademiai Kiado, Budapest, 1978, pp.863-880.

3. Yavuz, A.T., Divrigi Ulu Camisi Hunkar Mahfeli Tonozu in Divrigi Ulu Camii ve Darii§§ifasi, ed. Y.Onge, Ate§, S.Bayram, Ankara 1978, pp. 137-154.

4. Tukel (Yavuz), A., Selguklu Devri Anadolu Mimarisinde Suslu

Tonoz Kullam§i, METU, Faculty of Architecture, unpublished dissertation, Ankara 1971.

5. Unal, R.H., "Igdir Yakinlannda Bir Sel^uklu Kervansarayi ve Dogubayazit-Batum Kervanyolu Hakkinda Notlar" in Istanbul

Universitesi Sanat Tarihi Yilhgi III, Istanbul, 1970, pp.7- 15.

6. Gabriel, A., Monuments Turcs d'Anatolie, Vol. I, Paris 1931, p.93, Fig. 61.

7. Cuneo,P., Architettura Medievale Armena, Roma, 1968, pp. 152- 153.

8. Hautecoeur,L., Wiet,G., Les Mosquees du Caire, Paris 1932, p.277.

9. Sauvaget, J., Aleppo, Paris, 1941, p. 142, Fig. 52.

10. Acland, J.H., Medieval Structure: The Gothic World, Toronto and Buffalo 1972, pp.219-238.

Structural Repair and Maintenance of Historical Buildings 177

1. Sivas Keykavus Darii§§ifasi - star vault over the fifth bay

from the West in the south riwaq - plan with coursing.

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2. Sivas Keykavus Daru§§ifasi - star vault over the fifth bay from, the West in the south riwaq - section.

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6. Erzurum Hatuniye Medresesi - star vault of the east eyvan plan of the geometric set-up.

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8. Alara Han - star vault of the fountain eyvan - plan with coursing.

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9. Kayseri-Sivas Sultan Han - star vault of the entrance eyvan plan with coursing.

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10. Divrigi Turan Melik Darti§§ifasi - star vault of the first floor

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11. Divrigi Turan Melik Daru§§ifasi - star vault of the first floor space over the entrance - section.

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12. Divrigi Turan Melik Darii§§ifasi - star vault of the main eyvan - plan with coursing.

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1. Bursa Ye§il Cami - star vault of the room at the NW corner (A.T.Y. 35/6194)

2. Sivas Gbk Medrese - star vault of the entrance eyvan (A.T.Y 35/2672)

Structural Repair and Maintenance of Historical Buildings 191

3. Erzurum Hatuniye Medresesi - star vault of the east eyvan

(A.T.Y. 35/4518)

4. Han near Igdir - vault of the entrance (R.H.Unal)

192 Structural Repair and Maintenance of Historical Buildings

5. Divrigi Ulu Camisi - vault over the fourth bay from the East in the south horizontal aisle (A.T.Y. 35/2546)

6. Divrigi Ulu Camisi - vault over the second bay from the East in the second aisle from the South (A.T.Y. 35/2536)