Is a former Orthodox Patriarchal Basilica, later a mosque, now a Museum in Istanbul, Turkey. Since the date of its inauguration in 360 until 1453, served as Greek Patriarch of Constantinople Cathedral, except between 1204 and 1261, when it was converted into a Roman-Catholic Cathedral under purview of the Latin Patriarch of Constantinople of the Crusader West of Latin rite. The building was a mosque in May 29, 1453 until 1931, when it was secularized. Opened then as a museum.