Cliffs rise steeply from its western edge, up to the summit of Foel Grach, and down from which most of its feeder streams flow.

A small dam was built at its northern end in 1887, but this was deliberately breached in 1970.

The lake acts as a reservoir for the Llandudno area.

Less than a kilometre to its north lies the larger Llyn Dulyn.

The outflow from the lake is called Afon Melynllyn, this stream flowing north-east to join Afon Dulyn, itself a tributary of the river Conwy.