The first castle on this site, built in 1261, faced its companion, Carlingford Castle, across the mouth of the lough. It was then a two-story rectangular tower surrounded by a curtain wall with corner towers. Very little of that survives; most of what you see is from the 14th century. It served as a royal garrison until it was destroyed by Cromwell’s forces in 1652. Opening times are somewhat unpredictable, so if you want to see inside, call ahead.