Llyn y Fan Fawr outflow is to the River Tawe. Much of the land around the lake is peaty and thus wet underfoot. Llyn y Fan Fawr Llyn y Fan Fawr (Welsh: 'lake of the big peak') is a natural lake in the county of Powys, Wales. It lies at the foot of Fan Brycheiniog, the highest peak of the Black Mountain (Welsh"Y Mynydd Du") range within the Brecon Beacons National Park. Created as a result of glacial action, it is one of the largest glacial lakes in southern Wales. The lake is roughly rectangular in shape with its long axis oriented roughly north-south.
Pen y Clawdd Castle Pen y Clawdd Castle Pen y Clawdd Castle is a ditched mound with a double moat, roughly circular in shape, with a diameter of approximately 28m to 30m and about 2.4m high. The castle is in Llanvihangel Crucorney, about five miles to the north of Abergavenny, Monmouthshire, in south east Wales and lies between the Usk and Monnow rivers. The mound was designated a scheduled monument in 1950 and described as a defensive medieval motte. The castle mound is adjacent to Pen-y-Clawdd Court (a Grade I listed building), a stable and cowshed with adjoining range, and a barn, all of