The ramparts of Saint-Malo form a fortified enclosure 1,754 metres long, punctuated by eight gates with access stairs, three posterns, and three bastions. Built in granite, they are decorated with machicolations and flanked by several towers (here the Bidouane tower). Built in the 12th century, well before the golden age of the corsair town, they were rebuilt after the great fire of 1661. In the 18th century, the ramparts were extended by the military engineer Siméon Garangeau, appointed by Vauban, who increased the surface area of the city from 16 to 24 hectares. The ramparts of Saint-Malo have been listed as historical monument since 1886.