One of the most impressive fortresses in England, sitting on the chalk cliff above the harbour with a commanding view of the Channel. The medieval keep was built by Henry II in the 1180s, but the site has been fortified since the Iron Age — making it one of the longest continuously used defensive sites in the country. The keep has been restored to its medieval appearance, with rooms furnished as they might have looked in the 12th century.
The tunnels beneath the castle are the highlight for many visitors. Originally dug in the Napoleonic era, they became the nerve centre of Operation Dynamo in 1940 — the audacious evacuation of the British Expeditionary Force from Dunkirk. You can walk through the underground command rooms and hospital as they appeared during the war. Also within the castle grounds: a Roman lighthouse (one of the tallest surviving Roman structures in Britain) and the Saxon church of St Mary in Castro beside it. Allow at least half a day.