King John’s Castle was built in the 12th century on a rocky outcrop overlooking Carlingford Lough. The Castle dominated the Lough, the harbour and the developing town. This was the first stone building built in Carlingford and under the shadow of the castle the town grew. It is said that King John of England stayed here for a few days in 1210 AD.
The original Castle consisted of an enclosed D-shaped courtyard with two rectangular towers at the entrance. The eastern part of the Castle was built in 1261 and this included a number of rooms and a great hall.