A rescue excavation was necessary in the so-called Sibyl’s cave. This provided the opportunity for the collection of data relating to the history of the monument and for a revision of its “reading” and interpretation. According to the most recent and reliable hypotheses this is the tunnel constructed by the Samnites between the end of the 4th and the beginning of the 3rd century B.C. for strategic-military purposes in anticipation of the war with Rome. Cut into the tufa bedrock at the base of the acropolis with the openings facing west, it is situated outside the line of the western part of the town’s fortifications, as an extramural defence. Modifications made during the Roman period, during the civil wars, perhaps in order to use it as a quarry, lowered the floor level and inserted a square room, excavated to the east, half way along the tunnel’s length. Three cisterns opened onto this room and below the latter there was originally a channel cut into the tufa which carried the water from the cisterns. In the Christian period this area was converted for funerary use, as attested by the masonry built “a cassone” tombs on the bottom of the cisterns. Analysis of the complex stratigraphy and of the acquired data indicates that use of the cisterns and tunnel for hydraulic purposes was interrupted after the 1st century B.C. when the tufa channel in front was cut. This was then restored in the Byzantine period, during the Greco-Gothic wars, and substituted by another built of opus caementicium with a vaulted covering. The presence and the concentration of sixteen or seventeen carefully placed burials is to be associated with Christian practice. These “a cassone” tombs can be dated from the 5th to the 7th century A.D., however funerary use of the area must only have begun after the renewed use of the cisterns came to an end. The cult function must have involved Christians, both Cumani and Byzantines.