The last big cave is the largest on the itinerary, its irregular ceiling which follows the natural seams of the rock, up to a height of 14 meters, suggests that it is also the oldest.

When, in the 19th century, the great embankment that supports the street above was constructed, most of the tufa required was quarried from here.
Still visible are chisel marks made during the extraction of stone blocks and flaking of the rock due to the quarrying that has cancelled out most of the evidence of the Etruscan, Medieval and Renaissance past.

However, there still remain traces of an access stairway, on the highest part of the chamber, some niches of different periods, small channels and some vats, often retaining their plaster.

The most important discovery is maybe the base of a well in the centre of the chamber; the 19th century damage does not allow it to be establi-shed whether this was excavated to create a cistern, a grain silo or more tombs.
The use of well number two therefore remains a mystery.