Pen y Fan is the highest peak in South Wales, situated in the Brecon Beacons National Park. At 886 metres (2,907 ft) above sea-level, it is also the highest peak in Britain south of the Snowdonia mountain range.

The summit lies on a ridge stretching from Talybont Reservoir in the east, to the A470. 500 m west lies the subsidiary top of Corn Du, beyond which the terrain descends gently towards the Storey Arms on the A470. To the east, the ridge drops steeply to the col connecting it to Cribyn, the next mountain along the ridge. From Corn Du, a gentle ridge descends south towards Merthyr Tydfil.
Highly trained special forces troops utilise the area as part of a special forces selection training area (See "Fan Dance")

The mountain is used by the military for training and selection processes.

Pen Y Fan is formed of strongly glaciated Old Red Sandstone.

Tommy Jones Obelisk

On the route from the Storey Arms to the summit, a memorial obelisk commemorates a five-year-old boy who died in August 1900. The son of a Rhondda coal miner, Tommy lost his way near Cwm Llwch Farmhouse while visiting his grandparents, starting a twenty-nine day search which aroused nationwide concern. His body was found at the spot marked by the obelisk. Tommy had died from exhaustion and hypothermia or exposure, but how a small boy managed to climb so high remains a mystery.
The inscription on the obelisk reads, "This obelisk marks the spot where the body of Tommy Jones aged 5 was found. He lost his way between Cwm Llwch farm and the Login on the night of August 4, 1900. After an anxious search of 29 days his remains were discovered Sept. Erected by voluntary subscriptions. W Powell Price Mayor of Brecon 1901."

The obelisk, a useful landmark in misty conditions, was paid for by the proceeds of a memorial fund started when the jurors at the boy’s inquest waived their fees.

The search was used as the theme of the 1980 film, Tommy Jones.

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