Y Gyrn is a ridge on Pen y Fan, the highest peak in South Wales, situated in the Brecon Beacons National Park, within the county of Powys. Its height reaches 619 m (2032 feet). Between the summit and Corn Du is found Tommy Jones'Obelisk. Tommy was the son of a Rhonda coal miner and died from exhaustion and hypothermia or exposure. The obelisk is a useful landmark in misty conditions. The summit offers beautiful views of Bristol Channel on a clear day.