The church of St Dimitrios in the centre of Thessaloniki, close to the Roman Agora, is one of the most important monuments of the city. Initially it was a small temple, which was built on a Roman bath, where St Dimitrios was tortured. In the past, the church has been looted several times (by Saracens, Normans, Turks). From 1493 until 1912, it became a mosque. In 1917 it was almost totally destroyed by the big fire that destroyed a large part of the centre of Thessaloniki. In 1988 the church was declared a World Heritage Site by UNESCO. In the basement there is a crypt which leads to the place where the saint was imprisoned and tortured and is open to the public.