Olcaytu Türbesi (Sultaniye Kubbesi)

Soltaniyeh, in Zanjan province in north-western Iran, began around 1290 as a summer residence of the Ilkhanid ruler Arghun, chosen for its rich pastures and hunting grounds^2,3. In 1304 Arghun's son Öljeitü succeeded his brother Ghazan, enlarged the settlement and made it his capital, naming it Soltaniyeh, “the Imperial”^2,6. Together with Tabriz, it became a major trading centre on the routes between Asia and Europe². Its principal monument was Öljeitü's mausoleum, which UNESCO dates to 1302–1312¹. The tomb stood at the heart of a larger complex of buildings, of which little survives^1,5,7.

Öljeitü declared his allegiance to Shi'ism in the winter of 1307–08⁶. He is believed to have planned the building as a shrine for the remains of Imam Ali and Imam Husayn, brought from Iraq; the plan was dropped and it became his own tomb, though some scholars doubt this account^2,3,7. He died in 1316 and, according to the historian Hafez-e Abru, was buried in the crypt beneath the burial chamber^2,3. The city then declined; in 1384 Timur's army sacked it but spared the mausoleum². By the 17th century the city was in ruins, but the tomb still stood². In 1969–1979 a campaign run jointly with an Italian team stabilised the structure, and Iranian conservation work has continued since 1994².

The mausoleum is a huge octagon about 38 m across, with a rectangular burial chamber projecting on the south^4,7. Its walls, about 7 m thick, carry the dome without buttresses^2,3. The dome, about 25 m in diameter inside and some 50 m high, is covered in turquoise-blue faience, and eight slender brick minarets, purely decorative, rise around its base^1,2,3. A broad band of square Kufic script around the drum links the light-blue dome with the deep-blue muqarnas cornice below it^2,3. Below the cornice runs an outer gallery that does not open into the interior; its vaults carry carved and painted plaster patterns resembling contemporary book illumination^3,4.

UNESCO describes the dome as the earliest surviving double-shelled dome in Iran and an important reference for later Islamic domes¹. Encyclopaedia Iranica, however, records an earlier masonry double dome at Kharraqan (1067–68) and describes Soltaniyeh's thin shells as reinforced by arches between them⁵. Its upper galleries, unlike earlier arcades, were easily accessible⁵. The tomb served as a model for Timur's Gur-e-Amir in Samarkand and, ultimately, for the Taj Mahal in Agra^4,5.

The 360° photo is taken in the octagonal hall beneath the dome, which Encyclopaedia Iranica counts among the largest uninterrupted spaces of medieval times⁴. Each of the eight sides opens through a huge arch, with a two-storey arcade whose upper level forms a balcony overlooking the hall^2,3,4. Shallow muqarnas in the angles lead the walls into the circular base of the dome, about 25 m across². Two phases of decoration can be seen³. The first, of buff brick with blue glazed tile and Kufic inscriptions that include the name of Ali, survives in the large niches and in the spandrels of the arches³. In the second, from about 1313, a dado of light-blue hexagonal tiles was added and the surfaces above, including the dome, were plastered and painted with ornament and inscriptions^2,3,7. Much of the interior decoration survives¹.