This entrancing little church with a commanding view of the city was supposedly built about AD 500 in honor of Galerius's daughter, who was secretly baptized while her father was away fighting. It was later converted into a mosque, and at some time its west wall—the traditional place of entrance (in order to look east when facing the altar)—was bricked up, so you enter Osios David from the south. No matter; this entirely suits the church's rather battered magic. You can still see the radiantly beautiful mosaic in the dome of the apse, which shows a rare beardless Jesus, as he seems to have been described in the vision of Ezekiel: Jesus is seen with a halo and is surrounded by the four symbols of the Evangelists—clockwise, from top left, are the angel, the eagle, the lion, and the calf. To the right is the prophet Ezekiel and, to the left, Habakuk. To save it from destruction, the mosaic was hidden under a layer of calfskin during the iconoclastic ravages of the 8th and 9th centuries.
Plastered over while a mosque, it seems to have been forgotten until 1921, when an Orthodox monk in Egypt had a vision telling him to go to the church. On the day he arrived, March 25 (the day marking Greek independence from the Ottomans), an earthquake shattered the plaster, revealing the mosaic to the monk—who promptly died.