Corn Du

Corn Du
Pen y Fan from the summit of Corn Du
Highest point
Elevation	873 m (2,864 ft)
Prominence	28 m (92 ft)
Parent peak	Pen y Fan
Listing	Nuttall
Naming
Translation	Black Horn (Welsh)
Geography
Location	Powys, Wales
Parent range	Brecon Beacons
OS grid	SO012215
Topo map	OS Landranger 160

Corn Du is a mountain immediately to the southwest of Pen y Fan and the second highest peak in South Wales at 873 m (2,864 ft), situated in the Brecon Beacons National Park. The summit itself is marked by a well structured Bronze Age cairn with a central burial cist like that on nearby Pen y Fan. The two summits are visible from great distances owing to their height above the surrounding moorland, and are famous landmarks. The views from the peaks are also panoramic and very extensive, the Black Mountain (range) and Fforest Fawr being especially obvious to the west. Mynydd Epynt is visible to the north behind the county town of Brecon, and other parts of the escarpment to the east.

The summit is often crossed on the way to Pen y Fan, and forms part of a well-known circuit of the Beacons. It offers good views down into Cwm Llwch and across the Usk valley to Brecon as well as east towards the Sugar Loaf, Monmouthshire above Abergavenny.Tommy Jones' Obelisk is found on its western flanks, in between the summit and Y Gyrn. All of the surrounding moorland is open to access, but crossing the many peat bogs is difficult and the paths are well engineered and maintained by the National Trust.

The summit is very similar to that of Pen y Fan: flat and anvil shaped. It is similarly formed from the relatively erosion-resistant Devonian age sandstones from the Upper Old Red Sandstone known as the Plateau Beds. The rock strata are clearly visible at the edge of the escarpment, where they form a resistant edge to the cliff. The same strata are visible all along the escarpment facing north, as well as the rearward edge facing south-east and lying behind the main peaks. The same Plateau beds recur in the Black Mountain (range) to the west, and cap the summits of Picws Du and Fan Foel, as well as forming steep cliffs below the peaks.