The users of Roman baths always found three environments in the building, no matter how big or important it was: the frigidarium, the calidarium, the tepidarium (fig. 1).

Fig. 1 - Ostia, Baths of the Forum (II cent. A.D.). In yellow the tepidaria (from Pavolini 1983, p. 106).

The latter were usually quite small and were to avoid Baths users suffering an abrupt transition from an overheated environment to cold ones and vice versa (fig. 2).

Fig. 2 - In green the tepidarium of Baths II (from Bacco, Serra 1998, re-worked by C. Tronchetti).

The tepidarium is recognisable because it is not heated directly by the oven, like the calidarium, but with hot water which passed under the floor and through wall cavities.

The tepidarium of the Baths of Fordongianus is in a bad state of repair (figs. 3-4) and we can only realise the function held because of its position on the route.

Fig. 3 - Passage from tepidarium to calidarium (photo by Unicity S.p.A.).

Fig. 4 - Wall of the tepidarium with evident signs of the bad erosion that has bared the wall's inner structure (photo by Unicity S.p.A.).