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 Pond Pen-y-fan Pond Pen-y-fan Pond is a man-made reservoir built around 1794-6 as part of the engineering works for the Crumlin Arm of the Monmouthshire Canal. The reservoir was used to maintain the water level in the canal. The reservoir is formed by a large earth dam with stone facings, forming banks on three sides of a gentle slope. The outlet to the canal feeder forms a stone-lined, oval tunnel and a valve chamber is set into the bank above. Pen Y Fan Pond Country Park features the reservoir, and provides a circular walk around the lake, and minimal facilities for