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 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. The building was converted into a museum in 1935 and returned to the role of mosque in 2020.