Marchlyn Mawr
Marchlyn Mawr reservoir is a high level lake in Snowdonia behind Elidir Fawr mountain. It is used as the high level water source for Dinorwig power station, a closed-loop pumped storage hydroelectric generating facility.
It is said that nearby lies the cave containing Arthur's treasure, a source of bedazzlement to the wanderer who sees it, and of disaster to the pilferer who touches it. The lake itself lies in between two mountains Carnedd y Fillast and Elidir Fawr and lies at a height of 636m above sea level and the reservoir took four years to build. The reservoir holds about of water. From the reservoir, a diameter tunnel runs for to a diameter vertical shaft. From the bottom of the shaft, a diameter tunnel leads to the power station, away.
It is possible to cycle up the road to the reservoir but a gate at the bottom prevents cars from driving on the road.
