Llyn Stwlan is an elevated reservoir located 1,600 feet up in the Moelwynion mountains of Eryri National Park (Snowdonia), North Wales. When electricity demand is high, the dam releases water down the mountain to turn turbines inside the Ffestiniog Power Station. During off-peak hours, the system pumps the water back up into Llyn Stwlan. Surrounded by rugged peaks, the area is heavily influenced by the region's historic slate mining.
Llyn Cwmorthin sits at the heart of one of Wales's most dramatic industrial landscapes. Beneath its dark waters lies part of a vast flooded network of slate workings, while the surrounding valley is dominated by towering waste tips and the remains of the quarry that once employed hundreds of men.
Along the shoreline, a series of distinctive stone projections and embankments mark the former industrial infrastructure associated with the quarry and Lake Mill. Climbing the old slate paths above the quarry reveals views across to the hydroelectric Ffestiniog Power Station and the decommissioned Trawsfynydd Nuclear Power Station.
