The church of the patron saint of Thessaloniki was built on the ruins of a Roman bathhouse where, according to tradition, St Demetrius was martyred in 303. The first church of the 4th century was replaced by a five-aisled basilica that was burnt down in the earthquake of 620. It was soon restored, but suffered the same fate in the great fire of 1917. After many years of work it was restored to its present form and returned to worship in 1948. The church of Agios Dimitrios is a gallery of ten centuries of Byzantine architecture and art. The nine surviving mosaics date from the 5th to the 9th century. The relics of Agios Dimitrios, which were kept in a monastery in Italy, were returned to the church in 1978. The Crypt, beneath the Holy Step, was the centre of the cult of Agios Dimitrios’ myrrh-burial. The crypt houses an exhibition of sculptures from the history of the church. In the chapel of Agios Euthymios, excellent frescoes are preserved. The fresco was painted in 1302-1303 at the expense of a Byzantine official and is attributed to the great painter Manuel Panselinos and his workshop.