The Citadel of Besançon is one of the twelve Vauban fortifications designated as a UNESCO World Heritage Site, and it is among the most impressive of them. Built between 1668 and 1711 on a rocky promontory 118 metres above the Doubs, it commands a complete view over the horseshoe bend of the river that encloses the old city below.
The citadel houses four museums: a natural history museum, a regional folk museum (the Musée Comtois), a museum of resistance and deportation commemorating Franche-Comté's role in World War Two, and a zoo. The resistance museum is the most powerful of the four — the citadel served as a Nazi prison during the occupation, and the executions carried out here are documented in considerable detail. The zoo, somewhat incongruously, occupies the same grounds and is popular with families.
Allow at least two to three hours to do the complex justice. The walk up from the cathedral is steep; there is a bus service for those who prefer not to climb.