The Hagia Sophia is part of the UNESCO World Heritage site in Istanbul. For almost a millennium after its construction, it was the largest cathedral in all of Christendom. It served as a center of religious, political, and artistic life for the Byzantine world and has provided us with many useful scholarly insights into the period. It was also an important site of Muslim worship after Sultan Mehmed II conquered Constantinople in 1453 and designated the structure a mosque. It would remain a mosque until being converted into a museum in the 1930s.