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Dome in Iranian Architecture
By: Bernard O'Kane
The Sasanian and early Islamic periods
The dome on squinches first appeared in Persia in the Sasanian period in the palace at Fîrûzâbâd (q.v.) in Fârs and at nearby Qal´a-ye Dokhtar, both erected by Ardašir (224-40) in the early 3rd century. Although the dome chambers at these sites are impressive in size, their conical squinches (arches across the corners of a cube, forming a zone of transition) are crude in design and execution (Plate I). The rubble masonry was so haphazardly applied that it is difficult to distinguish the outer edges of the squinches from the corbeled walls between them. The extreme thickness of the walls in proportion to the height of the dome is another indication that these chambers stood at the beginning of the series. There is no evidence of precursors. Roman domes on circular bases or smaller domes on pendentives obviously sprang from a different tradition (Ward-Perkins, p. 338). Evidence for the simpler pitched-brick dome exists from as early as the 3rd millenium B.C.E. in Mesopotamia (Reuther, p. 501), but the absence of any known intermediaries between them and the Fîrûzâbâd domes, even from the Parthian period, attests to the originality of the Sasanian examples.
The most numerous surviving Sasanian domes are those over chahârtâqs, frequently the central chambers of fire temples. It is in the large dome of the structure variously identified as a palace and a fire temple at Sarvestân in Fârs that two constant features of later dome design first become apparent: the use of lighter materials, in this instance brick, for the dome itself and decorative emphasis on the zone of transition, which at Sarvestân is carefully set off by dogtooth moldings above and below and lightened by four windows between the squinches. The squinches are also more clearly articulated, each consisting of intersecting segments of two tunnel vaults (Bier, figs. 24-28). These features are, however, consistent with an early Islamic rather than a late Sasanian date for Sarvestân, a possibility also mooted for several chahârtâqs.
The survival of the dome on squinches in the Islamic period may have been encouraged by the transformation of several chahârtâqs into mosques, documented in a few instances. The building of isolated dome chambers to serve as mosques ("kiosk mosques") may have followed, though the evidence comes not from the usually cited congregational mosques of major cities but from a few, mostly Saljuq examples in small villages in Khorasan.
It was the appearance of the domed mausoleum that was to prove most important for the development of the dome in early Islamic Persia. Despite initial Islamic hostility to tomb structures, by the 10th century several had probably been built by the ´Abbasid caliphs for themselves (Allen). Domed tombs had also been erected over the graves of many Shi´ite martyrs (Blair, 1983, pp. 83-84), and the respect paid to them by pilgrims may well have hastened the spread of the form. Two early mausoleums in Transoxania stand out: that of the Samanids in Bukhara (before 331/943) and the ´Arab Atâ at Tîm (possibly 367/977-78), between Bukhara and Samarqand. In the zone of transition in the former the squinches are of the same width as the arches between them, resulting in a regular octagonal plan at this level; this scheme was followed in virtually all later examples. At Tîm the zone of transition is further unified by trilobed squinches composed of large moqarnas (oversailing courses of niche sections) separated by trilobed arches. This mausoleum is also the earliest extant to incorporate a pîštâq (an arched portal projecting vertically or horizontally from a facade), a feature that also became usual in domed-square mausoleums but that, even at this early stage, often made its impact at the expense of the dome.
Tomb towers represent another tradition in Persian mausoleums; many survive from the beginning of the 11th century onward. They are circular or polygonal in plan, thus reducing the importance of the zone of transition, and they frequently have conical roofs masking interior domes. Although the domes of the earliest tomb towers are plain, the shafts often display the inventive decorative brickwork of the period, as at the Pîr-e ´Âlamdâr (417/1026-27) and Chehel Dokhtarân (446/1054-55) at Dâmghân (q.v). Two other notable examples are at Kharraqân on the Qazvîn-Hamadân road 33 km west of Âb-e Garm (460/1067 and 486/1093); the earlier had the first masonry double dome known from Persia.
The Saljuq period. The introduction by the Saljuqs of a maqsûra (enclosure) in front of the mihrab of the hypostyle mosque helped to transform the skylines, characteristically punctuated with domes, of Persian towns. Although in the early Islamic period dome chambers may have been used for small neighborhood mosques, it was only after the vizier Nezâm-al-Molk introduced the domed maqsûra (ca 479-80/1086-87) in the congregational mosque at Isfahan that dome chambers on the qebla become the norm in Persian congregational mosques. It was the largest masonry dome in the Islamic world in its time and embodied a new form of squinch, in which a barrel vault above two smaller quarter domes was substituted for the weaker central unit of the squinch at ´Arab Atâ. The classic status of this squinch form is clear from numerous copies, not only in the Isfahan oasis (Barsîân, Ardestân [qq.v.], Zavâra), but also in Khorasan (RebâtÂ-e Šaraf) and Transoxania (Yarty [Yortî] Gonbad; Karriev et al., pp. 88-89). At the Isfahan mosque Nezâm-al-Molk's rival Tâj-al-Molk built a second dome chamber (481/1088) on the axis opposite the southern chamber, for purposes that are still unclear (see Blair, 1992, pp. 166-67). It is justly famous as the cynosure of Saljuq domes (Pope). The emphasis on verticality and on lightening the walls of the lower square became typical of Il-khanid dome chambers. The interior of the dome of Tâj-al-Molk is patterned with interlacing ribs that form pentagons and five-pointed stars, among other geometric figures. This arrangement represents a considerable technical advance over the eight ribs in the southern dome and could well have inspired subsequent designers of patterns for this hitherto neglected surface. The much smaller domes over the bays of the hypostyle portion of the Isfahan mosque also display a wealth of geometric ornamentation (Galdieri, I, pls. 60-62).
The numerous Saljuq dome chambers of northwestern Persia usually have much simpler zones of transition than those at Isfahan but, perhaps in compensation, are abundantly decorated with carved stucco and are also sometimes articulated on the exterior (Hillenbrand, 1976). This concern is most apparent in the largest Saljuq domed chamber, the tomb of Sultan Sanjar at Marv. Although the dome is decorated on the interior with a system of intersecting ribs, the squinches and lower walls are plain. The exterior zone of transition received the greatest emphasis, with the squinches disguised by alternating large and small arches, echoed by smaller superposed arches at the base of the double-shelled dome. Stucco work on the soffits of the main arcade, probably by the same artisans who had earlier worked at Rebât-e Šaraf (cf. Cohn-Wiener, pl. VIII; Hill and Grabar, fig. 546), underlines the new importance of this zone.
The Il-khanid period. The dome chamber of the congregational mosque in Varâmîn provides an example of changes in Persian domes in the Il-khanid period. Its taller proportions result primarily from the increased height of the zone of transition, with the addition of a sixteen-sided zone above the main zone of moqarnas squinches. Extra light enters through eight windows in this upper tier, although, as the Persian climate necessitated avoidance of sunlight during most of the year, architects of Persian dome chambers never aspired to the walls of light that characterized Ottoman examples.
The major Il-khanid domes were those of the mausoleums of GÚâzân Khan at Tabrîz and Öljeitü (UÚljâytû) at Soltânîya, each at the center of a larger complex of buildings. GÚâzân's mausoleum was twelve-sided; although it is no longer extant, its magnificence may be judged by that of ÖÚljeitü, which was built to rival it. The dome of Öljeitü's mausoleum is 50 m high and nearly 25 m in diameter, dimensions unsurpassed in later Persian examples. The decoration of tile, stucco, and painting (the last forming part of a remodeling of the interior; Blair, 1987) is the finest surviving from the period. The thin double-shelled dome was reinforced by arches between the shells. Galleries on the upper part of the octagonal exterior differ from earlier arcades in that they were easily accessible. They were the first in a series that can be traced through Timurid and Shaybanid examples to a culmination at the Taj Mahal in Agra.
In the Il-khanid period tomb towers mirroring the splendors of Öljeitü's mausoleum proliferated. Several have moqarnas domes. This feature was found in brick at the Saljuq congregational mosque at Sîn, and an example covered with painted plaster in the congregational mosque at Nâ÷în may date from as early as the 10th century (Hillenbrand, 1987, fig. 11). In Il-khanid examples they usually consist of plaster shells masking the underlying structures. The finest example is probably that at the tomb of ´Abd-al-Samad in Natanz. The form may have been adopted from the tomb of Shaikh Sohravardî, founder of the order to which ´Abd-al-Samad belonged, near Baghdad (Blair, 1986). In the Mesopotamian examples (that of Imam Dûr at Samarra, 478/1085-86, is the earliest) the moqarnas are frequently expressed on the exterior as well. This form is occasionally found in Persia, for example, at the emâmzâda (q.v.) of Mîr Mohammad on Kharg island, dated 738/1337 (Watson, p. 187). A plaster slab discovered at Takht-e Solaymân in Kordestân is incised with a plan of the moqarnas vaulting for a room restored by Abaqa Khan (671-74/1271-74; Harb).
The dome over the chamber adjoining the Do Manâr Dardašt in Isfahan marks a major advance in dome design. If contemporary with the gravestone of Soltân-Bakht Âqâ inside (753/1351-52; Honarfar, Esfahân, p. 317), it is the earliest known example of a double dome in which the inner and outer shells have substantially different profiles. It has been claimed that the dome of the Soltânîya complex in Cairo (probably built by Sultan Hasan, ca. 1356-60) was the origin of this form, which then spread to Persia (Meinecke, p. 175), but the interior buttressing at the Soltânîya complex betrays the influence of a brick tradition, suggesting a Persian origin. The trend toward taller drums continued in the Timurid period, finally reaching the inordinate proportions of the ´Ešrat-khâna in Samarqand (ca. 869/1464). One factor responsible was the increasing height of pîštâqs, which at the boq´a (shrine) of Zayn-al-Dîn Khúâfî at Tâybâd (848/1444-45) led the architect to abandon the outer shell of the dome altogether (Plate II). Where the drum was retained, however, it usually rose straight from a lower square, resulting in the loss of an external zone of transition.
There were two divergent trends in the interior decoration of domed chambers from the Saljuq period onward. The most prominent was the substitution of plain or painted plaster for brick. The other was increased use of tilework. A spectacular early example of nearly complete tile revetment is the dome chamber of the congregational mosque at Yazd (765/1364; Plate III). The same craftsman's signature appears in the dome of this monument and in the congregational mosque at Sâva (O'Kane, 1984, p. 84). The interiors of several of the mausoleums in the Šâh-e Zenda in Samarqand (e.g., that of Šâd-e Molk, 773/1371) are totally reveted in tilework.
In the 15th-17th centuries. After the turn of the 15th century the Timurids built very few freestanding mausoleums, attaching them instead to madrasas (religious schools), often in pairs. The dome chambers erected within these madrasas revolutionized the design of interiors, as in the madrasa of Gowhar âd at Herat (820-36/1417-33) and the madrasa at Khargerd (ca. 840-46/1436-43; O'Kane, 1987, nos. 14, 22). This change probably originated in 14th-century experiments with small lantern domes set at right angles to the main transverse vaults, from which arose the concept of using intersecting arches to support a dome with a diameter smaller than the width of the square below. The chamber was also modified, with a deep recess added to each side to produce a cruciform plan. The result was a much more fluid space than had been possible with the rigid tripartite division of lower square, zone of transition, and dome. In particular, the intersecting arches provide a visual link between the dome and the dado level, an illusion, as the thrusts are taken up by concealed masonry (O'Kane, 1987, pp. 108-09). In the madrasa of Gowhar Šâd the dome is actually a triple shell, the first of its kind; the intermediate dome presumably was added for reinforcement.
The tilework of the Qara Qoyunlû Mozaffarîya mosque (also known as the Blue Mosque, 870/1465) at Tabrîz is outstanding. Above a marble dado the whole of the interior of the dome chamber on the qebla was faced with dark-blue hexagonal tiles with stenciled gilding, creating a richness that was unparalleled until construction of the mosque of Shaikh LotÂf-Allâh in Isfahan (1012-28/1603-18), the quintessential Persian dome chamber. In the latter the blending of the square, zone of transition, and dome was achieved by unifying the first two, rather than the upper two, as in the Timurid examples with intersecting arches. The form of the squinches is plain, recalling those of Sarvestân and the Saljuq domes of northwestern Persia, but the way in which the framing arches and the enclosed tilework patterns continue in an uninterrupted sweep down to dado level was an innovation. The four identical arches between the squinches are edged by a bold twisted turquoise cable, lending the interior a new unity and simplicity. The exterior of the dome displays another innovation, the use of multiple levels of arabesque, interwoven with the brick ground with such finesse that it has often been mistakenly presumed that the ground, too, was glazed. The domes of the 17th-century Masjed-e Šâh and Mâdar-e Šâh madrasa in Isfahan show how effective a similar arabesque pattern can be against a light-blue tiled ground.
In Transoxania and neighboring regions the Uzbeks carried on the Timurid tradition of dome building with little change, though dome chambers were sometimes surrounded with axial ayvâns (q.v.) and corner rooms, as in the khânaqâh (Sufi monastery) of Qâsem Shaikh in Kermân (Golombek, fig. 16). Where these corner rooms are part of an octagonal plan and on two stories, as in the shrine of Khúâja Pârsâ at Balkh (ca. 1598), the form was a prototype for the major Indian mausoleums of Persian inspiration, that of Homâyûn in Delhi and the Taj Mahal. The domed tîmchas (markets) that survive at major intersections in Shaybanid Bukhara (McChesney) are among the earliest survivors of the type.
In vernacular architecture. Throughout Persian history the dome also played an important role in vernacular architecture. On many parts of the Persian plateau where wood is scarce whole villages with domed roofs are to be observed (Beazley, fig. 1). From Sasanian to Qajar times caravansaries (q.v.) were frequently constructed with the domed bay as the module. Domed cisterns (âb-anbâr, q.v.; Plate IV) and icehouses (yakchâls), still common sights in the Persian countryside (Beazley), are other reminders of the variety, pervasiveness, and permanence of the dome in Persian history.
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