You are taken into the impressive world of the fortress that Philippe Auguste built at the start of the 13C: along the route, you will discover the counterscarp wall, the 2. 60 m thick curtain, the foundations of the dwellings that were added by Charles V in 1360, the pier of the draw-bridge and the foundations of the castle's twin towers, the moat of the circular keep, known as the «big tower», and the royal objects found at the bottom of the keep's well are on show in two rooms.