The pool (natatio) of the baths is surrounded by a corridor running along all sides; on each side along the corridor five arches opened towards the pool (fig. 1).

Fig. 1 - Baths I; in green the portico (from Bacco-Serra 1998).

The southern portico is the only one preserved (figs. 2-4); the remaining parts have been lost. The traces left on the ground, showing imprints of pillars, comparison with other better preserved Roman baths building and the ideal continuation of the barrel vaults covering the pool make the reconstruction hypothesis just about certain.

The portico is built with an imposing opus quadratum and gets its light from three skylights open in the ceiling (fig. 5).

Fig. 2 - The southern portico of the pool (photo by Unicity S.p.A.).

Fig. 3 - Inside the southern portico (photo by Unicity S.p.A.).

Fig. 4 - View of the portico from the East (photo by Unicity S.p.A.).

Fig. 5 - Portico roof with skylights for lighting (photo by Unicity S.p.A.).