The citadel of Sisteron extends on a rock already fortified in Roman times when it housed an oppidum. In the Middle Ages, the Counts of Provence established their fortified castle made of palisades and precarious towers on this site to protect their territory from the neighboring County of Dauphiné. Between the two counties, the citadel dominates the cross valley in which the Durance flows and offers, over 93 mi (150 km), a view considered the most beautiful in Haute Provence.