Which mosque was built as a Christian church in the 6th century CE?

Hagia Sophia, officially the Holy Hagia Sophia Grand Mosque, is an important Byzantine structure in Istanbul and one of the world’s great monuments. It was built as a Christian church in the 6th century CE (532–537) under the direction of the Byzantine emperor Justinian I.

In subsequent centuries it became a mosque, a museum, and a mosque again. The building reflects the religious changes that have played out in the region over the centuries, with the minarets and inscriptions of Islam as well as the lavish mosaics of Christianity.

The Hagia Sophia combines a longitudinal basilica and a centralized building in a wholly original manner, with a huge 32-metre (105-foot) main dome. Art historians consider the building’s beautiful mosaics to be the main source of knowledge about the state of mosaic art in the time shortly after the end of the Iconoclastic Controversy in the 8th and 9th centuries.

Since 2018, Turkish president Recep Tayyip Erdoğan had spoken of reverting the status of the Hagia Sophia back to a mosque, a move seen to be very popularly accepted by the religious populace whom Erdoğan is attempting to persuade. While the Hagia Sophia has now been rehallowed as a mosque, the place remains open for visitors outside of prayer times. Entrance is free of charge.