Pen y Fan is the highest peak in South Wales, situated in Brecon Beacons National Park. At 886 metres above sea-level, it is also the highest British peak south of Cadair Idris in Snowdonia. It is the highest point of the historic county of Brecknockshire. The twin summits of Pen y Fan and Corn Du at 873 metres were formerly referred to as Cadair Arthur or 'Arthur's Seat'.