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.
Chwarel y Fan Chwarel y Fan Chwarel y Fan is a peak in the Black Mountains in south-eastern Wales. It is the highest rise on the long ridge which extends southeastwards from Rhos Dirion. The ridge continues southeastwards to the lesser summit of Bal-Mawr whose top is adorned by a trig point at above sea level. A further 1 km southeast along the ridge is the lesser top of Bal-Bach at a height of just over . Chwarel y Fan is the county top of the historic county of Monmouthshire, and is also the highest point in the current local government area of