On a promontory commanding a view of the North and South bays, the site of this castle appears to have been strategically significant since prehistoric times. Archeological digs here have uncovered evidence of fortifications dating from 500 BC, and there's some stonework from a 4th-century Roman structure thought to have been used to guard against sea raiders.
In 1136, a cliff-top stone fortress was built by the earl of Albermarle, and, in 1158, Henry II added the massive keep that dominates the ruins. Enormous curtain walls made the castle virtually impregnable, and it remained largely unscathed until Cromwell's cannons did their worst during the Civil War. Further demolition came in 1914, when German warships shelled the town, and again in 2012, when local vandals significantly damaged the Roman stonework. The castle also has a spectacular panoramic view of the coast.