formerGreek Orthodox patriarchal basilica (church), later an imperial mosque, and now a museum (Ayasofya Müzesi) in Istanbul, Turkey. From the date of its construction in 537 until 1453, it served as an Eastern Orthodox cathedral and seat of the Patriarchate of Constantinople,[1] except between 1204 and 1261, when it was converted to a Roman Catholic cathedral under the Latin Empire. The building was a mosque from 29 May 1453 until 1931. It was
