Dedicated to the patron Saint of the city, the majestic church of Aghios Dimitrios is one of the holiest pilgrimage churches of Christendom and the most important early Christian Church of Thessaloniki. It was built on the ruins of a Roman bath complex, the place where the saint was imprisoned and martyred in 303 AD.

The holy place of martyrdom, the Crypt, located beneath the transept of the church and in the late Byzantine years was the center of the Saint’s miraculous myrrh production. The miraculous myrrh gushing from the grave (that's why the Saint's nickname is Myrovlytis) and his reputation as a protector that protected Thessaloniki by the relevant invaders with His Divine intervention, overcame geographical boundaries of the city, and millions of pilgrims around the world who come to honor his grave for seventeen centuries. The Crypt is also open and visitable for pilgrims at the point of martyrdom and operates as a museum of antiquities Moreover, the access to the silver reliquary with the relics of St. Demetrius in the church is free, while the believers who will be in Thessaloniki during the days of celebrations for the feast of St. Demetrius (October 26), can watch the suggestive litany of the Saint's skull and relics on the city streets accompanied by military music band, members of the political and military leadership, local government and of course numerous believers (October 25).

The first church of Aghios Dimitrios was built after 313 AD. In 1493 it was converted into a mosque. After the liberation of the city in 1912 re-opened, but in 1917 the temple was almost destroyed by the great fire that burned the biggest part of the historical center of Thessaloniki. The church in its current form is a five-aisled basilica with narthex and transept, characterized by rich painting, mosaic and marble decorations, while in the southeast corner is annexed the chapel of Ag. Efthymiou.