The Roman bath along the via Traiana, 100 m NW of the Roman basilica, had already been investigated, in its northern part, during the ‘70. In 1997, 1998 and 2000 a new extensive research started, focused on the excavation of a wider area, in the southern part of the building discovered in 1972 by the Belgian team. This new investigation takes in account and merges the results both of the new and the past excavations. The amount of data available, the architectural analysis of the building and the comparisons with other similar known baths give the possibility to obtain a new plan of the building and work out new hypothesis about its functioning. Keywords: Imperial age, thermal rooms, concameratio, thermal path.