From the top of rue de la Citadelle, a rough cobblestone path ascends to the massive citadel itself, from where there's a spectacular panorama of the town and the surrounding hills. Constructed in 1628, the fort was rebuilt around 1680 by military engineers of the Vauban school. Nowadays it serves as a secondary school and is closed to the public.
If you've got a head for heights, descend by the steps signed 'escalier poterne' (rear stairway). Steep and slippery after rain, they plunge down beside the moss-covered ramparts to Porte de l'Échauguette (Watchtower Gate).