The Doric Building has four Doric columns on the front, which was 8,21 meters wide. It was built by Idrieus, son of Hekatomnos from Mylasa. The function of this building was a fountainhouse. In Roman times it was part of the East Bath complex, whose heating chamber (hypocaust) lies to the east. In Byzantine times it may have served as a source of water for the ritual washing before attending the Mass in the East Church.

On the map this must be the space north of the South Propylon.