The Church of Aghios Demetrios is one of the symbols of the historical city of Thessaloniki. The Church has five aisles, separated by columns. It has a long and dramatic history. The first church, a small oratory, was built in the 4th century on the ruins a Roman bath. You can see its remains in the crypt under the Church. A large, three-aisled basilica was built on the same site in the 5th century, which was burnt some years later. A five-aisled basilica was built on the ruins, which was converted into a mosque in the Late Middle Ages. It was restored to Christian worship in 1912 but was again destroyed in the Great Fire in the city in 1917. It was rebuilt and started to function again in 1949.