Built to a U-shaped plan with two wings enclosing the large basin. The lower part is built of more regularly shaped travertine blocks, while the upper part has blocks of varying dimensions, clearly taken from previous structures. On the basis of the architectural fragments is has been possible to create a reconstruction of the two orders, a lower one with exedras along the base and an upper one with straight stretches that are alternately projecting and recessed. Near the curves of the lower order, the niches were surmounted by tympana, conserved in the museum, bearing high quality busts of the principal deities of Hierapolis, embellished with various symbols and attributes: Selena, Jupiter, Juno, Artemis and Apollo.

It is at the east side of the Colonnaded Street, at some 200 meters from the theatre that is further to the east.