You can go around or penetrate through one of the large doors for this old town was fortified. In 1343, following the Guérande bag by Charles troops from Blois, Jean de Montfort asks the massive building of the city by developing the fortifications; order is given "to dig ditches and to close the city walls better."

The chamber in its current form covers approximately 1300 meters; it is pierced by four gates: Saint-Michel to the east, north Vannetaise, Bizienne west and south Saillé. In 1848, an additional opening is open to the southwest of the curtain: this is the gate of Tricot. The ramparts are classified as historical monuments in 1877.