The underground construction, better known as the underground barracks, is of military origin, although it is likely that it never came into operation. It was built between the late 1940s and early 1950s. The tunnel is completely excavated in the rock and lined with reinforced concrete; 371 meters long, it has a total development of 560 meters and has a difference in height of 49. It consisted of 22 rooms, including 4 in the upper gallery and 16 in the lower gallery, two of which were used as bathrooms. A staircase of 174 steps connects the two galleries together. Originally, the gallery had three entrances: the first was located on the top of the hill with a vertical course that connects with the lower part of the gallery; the second entrance (originally the main one) was located in the rock face of the hill, at a clearing facing east, and is currently inaccessible due to a collapse; the third entrance, the lowest, is located at the height of the terminus of the Line 5 Bus, on Cinquini Street; it was completed in 2010 and allows easier access to the gallery. Beginning in 1977, when the hill was demilitarized, it began to intrigue enthusiasts and cavers, who made it a destination for inspections and surveys.
