This enormous 5th-century structure honours Thessaloniki’s patron saint. A Roman soldier, Dimitrios was killed around AD 303 at this former Roman bath site, on orders of Emperor Galerius, infamous persecutor of Christians. The martyrdom site is now an eerie underground crypt , open daytime hours and for a Friday-night service. Dimitrios’s relics, returned from Italy in 1980, occupy a silver reliquary inside.
The Ottomans made Agios Dimitrios a mosque, plastering over frescoes. After the 1913 Greek reconquest the plaster was removed, revealing Thessaloniki’s finest church mosaics. While the 1917 fire was very damaging, five 8th-century mosaics survive, spanning the altar.