Sisteron is known locally as the “Gateway to Provence”. The Rocher de la Baume and its clue (cluse) are its most prestigious landmark. Composed of vertical limestone strata and world-renowned folds, this rock is considered a real curiosity by geologists. The limestone sediments deposited on the seabed at the end of the Jurassic period formed layers that were folded a first time at the end of the Secondary Era, then a second time during the surrection of the Alps in the Tertiary.

Sisteron’s citadel overlooks the town, built on a rocky spur. The citadel was a strategic lock on the road leading from the Alps to the Mediterranean. Listed as a historic monument, it is the town’s centerpiece. Jean Errard, military engineer to Henri IV, and later Vauban, left their mark on the citadel.