The extensive system of contromina for the defense of the covered terraces and paths of the Cittadella and some sections of the urban fronts is set in 1705, on the eve of the French siege, assigned to Antonio Bertola.
On the capital axis of each of the citadel's ramparts and external rivulets, the galleries were organized on two superimposed orders: a low capital gallery, deep between 12 and 14 meters, which from the inside of the citadel continued to the extremity of the avanspalti, one high up, between 5 and 7 meters, with access from the fly. Under the covered path, the magistral gallery secured the connection between the individual systems.
The construction of the countermine was also extended to the urban fronts of the stronghold directly exposed to the dangers of attack. The entire southern front of the fortress was involved in this operation, from the bastion of S. Barbara to the redoubt of Valentino, the Opera in Corno di Valdocco, the new extension of Porta Susina and the fronts of Vanchiglia.
With the demolition of the citadel, the countermines were abandoned in the subsoil. Partially reactivated as a shelter of the P.A.A. during the Second World War, they became patrimony of the Pietro Micca Civic Museum after the restoration works of 1958-1961.
