The Hagia Sophia was once a Christian Church. Today it is an Islamic Mosque. When it was a church, there were four angels known as the Seraphim Mosaic which protected the painting of Jesus Christ on the dome. When it became a Mosque, the faces of the angels were covered. Today, one of the four angels' faces is not covered. This photo shows all four angels. The angel with the uncovered face is at the bottom of this photo.