Dungarvan Castle

This is a polygonal 12th-century "shell keep" founded by Prince (later King) John in 1185. It replaced a motte-and-bailey and represents an early phase of Norman military architecture. When they replaced the previous timber palisade with masonry, they didn't trust the foundations to support the sort of massive curtain walls that later became the Norman style; so a high but lightweight shell of a wall was built with timber supports within. (England's Windsor Castle is of similar design.) There's also a corner tower and gate tower. In the 18th century a barracks was built within. This was burned down by the IRA in 1922 but rebuilt and acted as a police base until 1987; it now houses an exhibition on the castle history.