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 Bryn now stands, some 185 metres from the church and the Mŵd in the centre of the village. A high-status structure, associated with 13th and 14th century material and thought to be the royal llys with its domestic and administrative buildings, has been found in the valley bottom, on the other side of the river and some 185 metres from Pen y Bryn. It is by the mound known as y Mŵd, near which in 1811 visible remains were locally supposed to be the palace of the Welsh Princes. Pen y Bryn Pen y Bryn is a two-storey manor house, in