Required by the House of Savoy on which the city depended, they were financed by the bourgeois of Châtillon and built by the community from 1273. The ramparts were the first concern of the new town of Châtillon. The enclosure measured about 1000 meters. It was built of brick and lined with ditches that were filled with water thanks to the Chalaronne and the Relevant in case of danger. There were three fortified gates (Bourg, Villars, Lyon), these fortifications were a heavy burden for the Châtillonnais, but provided good protection.
There are few traces of these fortifications that surrounded the city at the time. Nevertheless, the tower transformed into the Central Chapel separating the rooms of the sick, men and women of the Old Hospital, the tower rehabilitated and currently occupied by the Hotel de la Tour and the beginning of the arches that extended the walls to theover the Chalaronne. This enclosure was pierced by three doors. Only remains the Porte de Villars. Fortified door, surmounted by a tower, with a drawbridge that was lowered only in case of danger, it is built entirely of brick. It allows us to imagine what the city was like in the Middle Ages.