Restored to its original form and constituent materials, the basement of the former Augustinian monastery was used by the monks to store foodstuffs, products arriving from the farms they owned and, presumably, also to shelter livestock. On the side facing Via delle Mura, it is still possible to recognise the ancient urban road layout and, on the back wall, a staircase leads to an underground chamber, in all probability the cellar as suggested by the chute where barrels were rolled, connected through a tunnel beyond the castle walls.

This passageway was providential for the escape of the population in the event of a siege, the same function it also had during the Second World War, when it served as a refuge for the population during the bombing of Certaldo on 16th January 1944, which caused death and devastation, including the collapse of part of Casa di Boccaccio.