Sisteron

Sisteron guards a defile where the Durance cuts between two rock walls, historically the gate between Provence and the Alps and the reason a fortress sits here. The citadel is a layered structure from the eleventh century onward with Vauban-era additions, climbing the ridge in walls, a chapel and a stepped underground stairway cut through the rock to a lower gate. Across the river the Rocher de la Baume shows limestone beds standing almost vertical, folded by Alpine pressure, striped like a set of blades. Allied bombing in August 1944 destroyed much of the old town and part of the citadel.

What you actually see

• The vertical strata - the Rocher de la Baume with beds folded upright.
• The layered citadel - fortifications from the eleventh century to Vauban.
• The rock stairway - an underground stepped passage through the ridge.
• The Durance gap - the defile the town was built to control.

When to go

April to October; the citadel closes over winter. Summer evenings bring open-air performances in the citadel theatre. The climb inside is steep with many steps.

Honest expectations

The citadel involves a lot of stairs and uneven ground. The old town was heavily damaged in 1944 and is partly postwar. Summer heat in the valley is strong.

Nearby

The Verdon lies southeast; Gap is north.