Llyn Cwm Llwch both Pen y Fan and Corn Du and indeed from the spur of Pen Milan to its west. Llyn Cwm Llwch Llyn Cwm Llwch () is a small lake or pool in the Brecon Beacons National Park in Powys, Wales. It is between 1 and 2 acres: much smaller than the two glacial lakes in the west of the Black Mountain (range): Llyn y Fan Fawr and Llyn y Fan Fach. It is of glacial origin, occupying a rock hollow beneath the peaks of Pen y Fan and Corn Du in the central Brecon Beacons. It is drained by the
Pen y Fan the Welsh Government. Toilet facilities are available at the site. A footpath connects the Storey Arms centre, bus stops and the Pont ar Daf car park to the path leading to Corn Du and Pen y Fan. The summit lies on a ridge stretching from Talybont Reservoir in the east, to the A470. About to the south-west lies the subsidiary top of Corn Du, beyond which the terrain drops at a moderate angle to the subsidiary top of Y Gyrn then more steeply to the Storey Arms on the A470. To the east, the ridge drops steeply to the col