The founding date of this church, a UNESCO World Heritage Site and the focal point of the city's Easter and Christmas celebrations, has been the subject of disagreements over the centuries. Ecclesiastics think it was built after the first Council of Nicea (AD 325), when Jesus was declared a manifestation of Divine Wisdom; other church historians say it was contemporaneous with the magnificent church of Ayia Sofia in Constantinople, completed in AD 537, on which it was
modeled. From its architecture the church is believed to date to the late 8th century, a time of transition from the domed basilica to the cruciform plan. The rather drab interior contains two superb mosaics: one of the Ascension and the other of the Virgin Mary holding Jesus in her arms. This latter mosaic is an interesting example of the conflict in the Orthodox Church (AD 726–843) between the iconoclasts (icon smashers, which they often literally were) and the iconodules (icon venerators). At one point in this doctrinal struggle, the Virgin Mary in the mosaic was replaced by a large cross (still partly visible), and only later, after the victory of the iconodules, was it again replaced with an image of the Virgin Mary holding baby Jesus. The front gate is a popular meeting spot.