The lake is flanked on one side by the mountain Elidir Fawr and the former slate quarry of Dinorwig.

Above the opposite bank are the hills of Derlwyn and Clogwyn Mawr and a rock formation known as the Lady of Snowdon, due to its resemblance to a human face.

Water is released into the lake from Marchlyn Mawr (the upper reservoir) to produce electricity during periods of peak demand.

This water is, in turn, pumped back to the upper reservoir using electricity purchased at off-peak periods.

Parts of the lake shore are designated as a Site of Special Scientific Interest for Glacial Geology.