You will enter into the impressive world of the fortress that Philippe Auguste built in the late-12C: along the way, you will discover the counterscarp wall, the 2.60m/8ft thick curtain, the foundations of the abode 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 royal artefacts found at the bottom of the keep's well on show in two rooms.