This unremarkable church sits atop the site of one of the most celebrated shrines to the Virgin Mary in Byzantium. But even before Constantine set foot inside the city walls, the spring located on this spot was considered sacred. Citizens of Constantinople made regular pilgrimages to the spring, and in the 5th century A.D., Empress Augusta Pulcheria, wife of Emperor Marcian, had a church built on the site. Sometime between A.D. 457 and A.D. 474, Emperor Leo I added a marble statue of Mary, from whose hands flowed the holy water of the spring, as well as a sacred pool. He later added a chapel to house the relics of the Virgin Mary, which included the holy robe stolen by citizens of Constantinople on a pilgrimage to Jerusalem and a gold and silver icon of the Virgin. This icon was paraded along the battlements when the city was under siege by the Avars in A.D. 626 and is credited with saving the city. According to another tradition, the Holy Shroud (of Turin) was brought here in A.D. 944. The church succumbed to the wrath of the iconoclast period, and later, to fire. The church, and indeed the entire complex of buildings, was destroyed by fire in 1434. A replacement chapel was built in 1867, and later other sections were added on.