There is a 26-meter-deep defensive moat that must be crossed in order to get to the castle. A drawbridge was once used to traverse this ditch, which has always been dry; today, a stone bridge constructed during the time of Philip II and an iron footbridge are used to do so.

The stones quarried for the castle's construction were used to excavate the moat, which is natural in origin. Some half-hewn ashlars that were never utilized can still be seen at the bottom of the moat, 23 meters down.

The moat's gully, which must have originally been a natural rock cut, was widened by Henry IV, then widened once more during Philip II's renovation of the castle. It was used to house bears and to gather stone for the construction of the castle's defenses during the reign of Henry IV.

At the southernmost point of the gully, to the left of the moat, you can observe a portion of it with the morphology that it must have had during Henry IV's reign and that Philip II's reformation did not enlarge.