Stronghold on the western side of the walls of Upper Colle, the Volterrana Gate constitutes a point of reference in the history of the evolution of defensive systems of the Medici period. Built in 1479 with the contribution of expert military architects like Francione, Giuliano da Sangallo, Francesco d’Angelo and Paolo di Francesco, it indeed presents several elements which we find hereinafter in the construction of fortresses. Two powerful round brick keeps embrace the tract of wall where the round-arched gate is sited. The entire system is equipped with a high scarp and protruding defensive elements set on triangular stone corbels and brick arches, while the middle area is marked by two cordons (protruding stone structures born to prevent the walls being easily scaled; in the 16th century, with the introduction of bastions, they were regularly adopted). The whole lot is crowned by a parapet with battlements and embrasures (apertures for cannons).