Qualche cenno sull'argomento:

The refuge is some one hundred and eighty metres in length. It runs parallel to and equidistant from  Viale Merello and Viale Fra Ignazio. The main entrance was from Via Don Bosco, in a wall of rock  in front of which now rises the Maria Ausiliatrice Ophthalmology Clinic. Some transverse corridors  of the tunnel, on average a few tens of metres long, gave access to the refuge through other  entrances in private courtyards on adjoining streets. These secondary entrances are now walled up.  Almost the entire length of the tunnel is lined with benches on both sides. Also along the tunnel we  find fourteen side rooms at more or less regular distances from each other and all opening on the  same side of the tunnel, with lengths varying from nine to three metres. Eight of these rooms have  benches on their long sides, similar to what we find in the main tunnel. Still in the tunnel, a few  metres from the main entrance, there is a room furnished as a bathroom. The tunnel was not built as  an air raid shelter during the Second World War, but was a part of an articulated network of  underground passages that still exist today, with the same dimensions and excavation  characteristics, that run underneath the entire northern side of the town, from the bastions of  Buoncammino to the area of the market in Via Pola. They were probably dug in the 18th century by  the Piedmont rulers outside the town walls for military purposes, probably as escape tunnels or as a  countermining structure. Most of this network of tunnels was quickly transformed into air raid  shelters for the civilian population at the beginning of the Second World War. The tunnels were  cleaned out, bomb-proof reinforced concrete double and triple entrances were installed and benches  were placed along the walls. The tunnel served its purpose well, and as the inhabitants of the quarter  recall, some families even set up housekeeping in the side rooms. At the end of the war the tunnel  was forgotten and the entrances, including the main one in Via Don Bosco, were walled up. This  has kept it almost intact up to the present day.