Between Provence and Dauphiné, dominating the cluse where the Durance flows, the Citadelle of Sisteron dominates the sky, crowning the town with its walls, bastions and keep. The view from here is breathtaking, stretching for 150 km and offering one of the finest vantage points in Haute Provence. It bears witness to eight centuries of architecture and history. The keep and sentry walk, built on the narrow rocky spine, date back to the 12th century. The tiered bastioned enclosures dating from the 16th century of the Vauban project, designed in 1692, only the powder magazine was built.
Major alterations were carried out on the north face in the mid-19th century. It was at this time that the magnificent underground staircase linking the fortress to the town was carved out of the rock.
Saint-Georges de Boscherville Abbey is a former Benedictine abbey. It was founded in about 1113 by Guillaume de Tancarville on the site of an earlier establishment of secular canons and settled by monks from the Abbey of Saint-Evroul. The abbey church made of Caumont stone was erected from 1113 to 1140. The Norman builders aimed to have very well-lit naves and they did this by means of tall, large windows, initially made possible by a wooden ceiling, which prevented uplift, although this was replaced by a Gothic vault in the 13th century. The chapter room was built after the abbey church and dates from the last quarter of the 12th century.
The arrival of the Maurist monks in 1659, after the disasters of the Wars of Religion, helped to get the abbey back on a firmer spiritual, architectural and economic footing. They erected a large monastic building one wing of which fitted tightly around the chapter house (which was otherwise left as it was).