Llyn Cwmorthin lies in a high, glaciated valley above the village of Tanygrisiau. Slate quarries were once worked in the surrounding Moelwyn mountains, and a community of quarry workers lived in the valley. The remains of their barracks and a chapel stand beside the path that runs beside the lake. The path starts from a parking area near a waterfall above the village. It climbs to a mountain pass and a junction of paths, from where walks can be taken to visit other lakes or the Moelwyn summits.
