Llyn Fawr

Llyn Fawr is a reservoir set high on the northern edge of the South Wales Coalfield uplands. It fills a glacial cirque that overlooks the Vale of Neath and the Cynon Valley. Craig-y-Llyn, a mountain designated as a Site of Special Scientific Interest, rises to the south. Less than a kilometre away lie the headwaters of the Rhondda Fawr and Rhondda Fach rivers. The reservoir also sits close to the sources of the River Corrwg and Nant Gwrelych. The site is important for its Bronze Age hoard discovered between 1909 and 1912. The hoard contains late Bronze Age weapons and tools, including an iron sword dated about 650 BC. Two bronze cauldrons and several axeheads were also found. The finds were placed in the lake as votive offerings. The hoard gave its name to the Llyn Fawr Phase, marking the end of the Bronze Age in Britain. The artefacts are now held by Amgueddfa Cymru – Museum Wales. Visitors reach the reservoir along paths that climb from the surrounding valleys. The water is bordered by steep slopes that once held glacial ice. Craig-y-Llyn’s slopes rise sharply above the western shore. The dam built in 1909 still holds back the expanded lake. A 1.25-mile tunnel under Craig-y-Llyn carries raw water to Ty’n-y-waun treatment works. The reservoir remains part of Welsh Water’s supply network for the Rhondda valley.