The large Roman spa above the limestone sinter terraces was erected in the 2nd century BC and rebuilt after the earthquake in 17 AD. Another devastating earthquake in 1334 led to the complete destruction of the town and the spa.

In 1984 the main building was restored and converted into an archaeological museum. The 3 main rooms of the bathing complex, the apodyterium (changing room), the frigidarium (cold bathing room) and the caldarium (hot bathing room), now serve as exhibition rooms. Parts of the former gymnasium now serve as a museum garden.
There are indications that the huge walls of the interiors were covered with marble. In the north and south of the main complex there are two main halls, which were mainly used for the private use of the emperor and for ceremonies.