The church of Agia Sofia as well as the church of St Dimitrios and Achiropiitos are the most important early Christian monuments of Thessaloniki. The church has many similarities with Agia Sofia of Constantinople. During the Forth Crusade it was converted into a catholic church (1204-1224) and into a mosque by the Turks (1523-1912). The church represents a transitional style between the domed basilica and the domed cruciform church.Excavations have revealed remains of both a Roman building and an Early Christian basilica beneath the church. In 1988 the church was declared a World Heritage Site by UNESCO.