Three successive walls protect the keep which stands on the highest point of a rocky outcrop (729m). The polygonal two-storey keep is comprised of a lower room and an upper Gothic hall whose vaulting rests on a central pillar. The unusual layout and lighting have given rise, as at Montségur, to interpretations related to solar symbolism. On the lower floor, to the north of the keep is a vaulted room that leads into an underground gallery and a blockhouse.