The Liberation Museum occupies Fort du Roule above Cherbourg. Its displays cover the city's capture in 1944, when the Allies needed Cherbourg's port badly enough to fight hard for it after the Normandy landings.
The history is useful, but the view may be even better. From the hill you can read the whole harbour: the town below, the naval installations, La Cité de la Mer, and the sweep of the Grande Rade.