Ffestiniog Power Station, Gwynedd, seen from across the Tan-Y-Grisiau reservoir

NOTES: Consisting of two reservoirs, this was the first major pumped storage facility in the UK. The upper reservoir is an enlargement of the natural mountain lake, Llyn Stwlan, while the lower reservoir was formed by damming the Afon Ystradau with a concrete dam. The power station, built of local stone, is situated on the west side of the lower reservoir.