Built in 1603 to defend the Duchy of Milan from its Grisonian enemies, it was named after the Spanish Governor Pedro Enriquez de Acevedo Count of Fuentes. It was erected in record time by the military engineer Gabrio Brusca and nobody ever dared to attack it until 1706, when the invaders were forced to surrender. It was besieged for the first time by the Austrians in 1746. The fort was subsequently destroyed by order of Napoleon Bonaparte.