The thermal bath areas that can be accessed from the passage area of the biapsidal hall start from the frigidarium, a space dedicated to cold baths, with an octagonal plan around which is arranged a
colonnade that would have supported the
and a dome, probably with an opening in the centre, which let in rainwater. All the walls of the frigidarium were lined with
, which also denoted its public use.
The healing and invigorating baths took place in the two swimming pools to the north and south used for swimming and immersion respectively.The elegance of the thermal bath environment is shown not only in the rich architectural structure and coverings, but also in the mosaics that adorn the floor of the octagon, enlivened by a brightly coloured marine thiasos with mermen, nereids and fisherman erotes.The fantastic mythological scene is enclosed by six apsidal niches with realistic themed depictions of mutatio vestis, or changing of clothes.