Visited this site last summer and although it involves a fair hike uphill it is easy enough to get to. Heading North along the A479 towards Talgarth you pass a pub on your right (can’t remember name). There is a parking area next to the pub with information boards. All you have to do is follow the fairly obvious path up hill. At the top are the scant remains of a castle which is said to be the highest castle in Britain – cracking views. From what I remember it took me about 20 minutes to reach the top.