The turquoise dome of Soltaniyeh rises above open pasture in Zanjan Province, marking the mausoleum of the Ilkhanid ruler Öljaitü. Built between 1302 and 1312, the monument survives from a city briefly created as an imperial capital by the Mongol dynasty that ruled Persia. Its extraordinary scale and interior decoration make it a pivotal work between Seljuk and later Timurid architecture.
The octagonal brick structure is surrounded by eight slender minarets and crowned by a dome roughly 50 metres high. UNESCO identifies it as Iran’s earliest surviving example of a double-shell dome: separate inner and outer layers achieve height, proportion and structural efficiency. This innovation became an important reference in the development of Islamic architecture across central and western Asia.