The Château de Brest is a castle at the entrance to the naval harbour that has served as a fortification on this spot since Roman times, though the current structure dates largely from the medieval and early modern periods. The towers and curtain walls were repeatedly strengthened from the 13th to the 17th century, and Vauban modified the defences in the 1680s when Richelieu's naval programme made Brest one of France's most important military ports.
Inside the château, the Musée de la Marine occupies several of the historic buildings and traces the naval history of Brest and France more broadly. The collection includes ship models, navigational instruments, and historical documents covering the Atlantic voyages, the Revolutionary and Napoleonic wars, and the two World Wars. The setting — medieval towers, a working military port on one side and the city rebuilt from rubble on the other — gives the whole visit an unusual depth.