The castle overlooking the village of Knucklas was completed in 1242 by Roger Mortimer. It was surrendered to the Welsh under Llywelyn the Great in 1262, destroyed and possibly never rebuilt although a mention exists in the early 14th century. By the time of Owain Glyndwr around 1400-08 it had certainly gone. The castle was a square shaped bastion with 4 corner towers. It contained some buildings at the E end and a gate stood in the W wall. Outside the walls were two level 'killing platforms' to the E and S, there may have been another to the W. The N side is protected by the steep drop of the hill. The area on top of the hill has larger scale defensive earthworks and it is not known as to whether these are contemporary with the castle serving as a fortified agricultural area, or the remains of a much earlier Iron Age hillfort.