Elizabeth Castle occupies a tidal island in St Aubin's Bay and is St Helier's most striking landmark — a sprawling fortification begun in the 1590s and extended over two centuries. At low tide you can walk out across the causeway in about fifteen minutes; when the tide comes in, an amphibious ferry runs from the waterfront. The crossing is half the fun.
The castle has a long history of sieges and near-misses. Royalist Governor George Carteret held it for the Crown throughout the English Civil War; Parliamentarian forces eventually took it by lobbing mortar bombs onto the rooftops. During the German Occupation (1940–45) the castle served as a gun battery, and you can still see the heavy concrete emplacements added by the Wehrmacht. Jersey Heritage runs the site and mounts historical reenactments through the summer — the period-costumed soldiers firing muskets on the parade ground are a crowd-pleaser.