The central magnet of Soltaniyeh's several ruins is the Mausoleum of Il-khan Öljeitü also known as Muhammad Khodabandeh , traditionally known as the Dome of Soltaniyeh in Soltaniyeh city , Zanjan Province .
The structure , erected from 1302 to 1312 AD , has the oldest double-shell dome in Iran . This erroneous view of the construction was made by Dieulafoy but is totally disputed by Andre Godard . In Godard's view it is a normal , if spectacularly large dome , with a thin skin on top for the faience and is in no way a double dome . Its importance in the Muslim world may be compared to that of Brunelleschi's cupola for Christian architecture . It is one of the largest brick domes in the world , just at the theoretical engineering limit for a brick dome and the third largest dome in the world after the domes of Florence Cathedral and Hagia Sophia . The Dome of Soltaniyeh paved the way for more daring Iranian-style cupola constructions in the Muslim world , such as the Mausoleum of Khoja Ahmed Yasavi and the Taj Mahal . Much of its exterior decoration has been lost , but the interior retains superb mosaics , faience , and murals . People have described the architecture of the building as “anticipating the Taj Mahal” .
The estimated 200 ton dome stands 49 meters (161 ft) tall from its base , and is currently undergoing extensive renovation .