Iranian archaeologists have discovered part of the gate and entrance to the Sultaniyeh Citadel, the biggest brick dome in the whole world.

“While experts were digging the ground to build a duct, they stumbled upon part of the entrance and gate, dating back to Il-Khanid dynasty (1256-1336), beneath the floor of a mosque,” said Mohammad Reza Ghorbanzadeh, project manager.

The 1.35-meter-high gate is made of wood and has a metal, probably bronze, cover whose patterns indicate it was built during the reign of Il-Khanids. It weighs over 9 kg.

The mausoleum of Uljaytu Khodabande was built in Sultaniyeh, near Zanjan, in 1304-13 (A.H. 703-13). The basic structure is an octagon about 80 feet (24.5 m.) across on the inside. At the base the walls are almost 23 feet (7 m.) thick, giving a total width of approximately 126 feet (39m). The interior height of the single dome is about 175 feet (about 53 m.).

Andre Godard has described this monument as “... the skillful, confident work of a great builder, a consummate technician who was at the same times an artist. Here is a dome with a span of 80 feet built solely of bricks, without any buttresses, pinnacles, or shoulders of any kind, which stands simply by virtue of a perfectly conceived and constructed profile.”

Details of the original glazed tile and fine, carved stucco in the main chamber evoke speculation as to why blue was so much preferred by the early Iranian artists. This is the earliest major monument in Iran in which color has been used for massive effects. The dome was covered with tiles of turquoise, while the facade was decorated in shades of deep blue. Stalactites adorn the cornice and increase the play of light and shadow. Through the arch the elaborate patterns on the walls of the upper galleries can be seen.

The upper galleries of the mausoleum of Uljaytu present vistas of painted and carved stucco designs that glow in shades of red. The brick walls were covered with a smooth surface of hard plaster into which the patterns were cut to a depth of about three-eighths of an inch (about a centimeter) and then painted with distemper. It is extremely likely that decorative details from illuminated manuscripts were used in the ornamentation of buildings.