The spa complex with adjoining Palästra is located in the west of the city on the way from the temple of Zeus to the stadium-theatre complex. It was built in the second half of the 2nd century AD.
The typical bathrooms heated by hypocaust systems such as apodyterium, frigidarium, tepidarium and caldarium were located in the middle of the magnificent building. A marble statue of the goddess Hygieia was placed in the frigidarium. The goddess Hygieia was one of the daughters of Asklepios. She is a goddess of health and is considered the patron saint of pharmacists.

In Byzantine times, the thermal baths were converted into a bishop's palace and became the episcopal centre of the city's early Christian community.