Carlingford was first settled by the Vikings, and in the Middle Ages became an English stronghold under the protection of the now-ruined castle, which was built on a pinnacle in the 11th to 12th centuries to control the entrance to the lough. King John spent a couple of days here in 1210 en route to battle in Antrim.
It's closed to the public, but you can ask at the tourist office about free tours during Heritage Week .
On the western side, the entrance gateway was built to allow only one horse and rider through at a time.
