The historic centre of Rivarolo is enclosed within the boundary walls traced by Vespasiano Gonzaga at the end of the 16th century, whose design was then implemented by his successors, Giulio Cesare and Scipione, in the early decades of the 17th century, whose three city gates with a single turreted arch have been preserved. A wall circuit for customs purposes as well for defence against the scourge of banditry: in the 16th century, to the dispatches of the vicars who, from Rivarolo, still complained about robberies, looting and murders committed by armed gangs of mobsters, the rulers replied with the issue of bounties and the organisation of horse-mounted teams entrusted to Campaign Commissioners who operated with “potestas ad modum belli et per horas”, i.e. applying summary justice, “sine strepitu et figura judicii”.
Its current appearance is attributable to the interventions carried out in the 1920s which eliminated the original sloping roof top. The interior features a succession of rooms connected by a small passageway.