Takht-e Soleymān is an archaeological site in West Azarbaijan Province, Iran from Sasanian Empire. It lies near the present-day town of Takab. The fortified site, which is located on a hill created by the outflow of a calcium-rich spring pond, was recognized as a World Heritage Site in July 2003. The citadel includes the remains of a Zoroastrian fire temple built during the Sassanid period and partially rebuilt as a mosque during the Ilkhanid period. This temple housed one of the three "Great Fires" or "Royal Fires" that Sassanid rulers humbled themselves before in order to ascend the throne.