[2] The basilica is famous for six extant mosaic panels, dated to the period between the latest reconstruction and the inauguration of the Byzantine Iconoclasm in 730.

Under the Latin Empire in 1206, the legate Benedict of Porto gave Hagios Demetrios to the canons of the Holy Sepulchre.

About 60 years later, during the reign of Bayezid II, the church was converted into a mosque, known as the Kasımiye Camii after the local Ottoman mayor, Cezeri Kasım Pasha.

[4] Other magnificent mosaics, recorded as covering the church interior, were lost either during the four centuries when it functioned as a mosque (1493–1912) or in the Great Thessaloniki Fire of 1917 that destroyed much of the city.

Black-and-white photographs and good watercolour versions give an idea of the early Byzantine craftsmanship lost during the fire.

Tombstones from the city's Jewish cemetery - destroyed by the Greek and Nazi German authorities - were used as building materials in these restoration efforts in the 1940s.

In the years that followed, the fountain acquired basins, from which the faithful could collect myron, the sweet-smelling oil produced by the saint's relics.

More specifically, in room I there are sculptures from the original 5th-century church and piers with relief decoration and capitals with four acanthus leaves.

In room II, in the saint's chapel, there are inscriptions documenting the history of the church, together with figural sculptures of the Middle Byzantine period.