It is held back by the 27 metre high Alwen Dam, which impounds the Afon Alwen, and is 8km downstream from Llyn Alwen.
It lies on the rolling Silurian moorland to the north-west of Mwdwl-eithin and about 10 km to the east of Betws y Coed.
Llŷn Peninsula | Tal-y-llyn | Tal-y-llyn, Gwynedd | Llyn-y-foel | Llyn Celyn | Tal-y-llyn, Anglesey | Llyn y Fan Fach | Llyn Padarn | Llyn Mair | Llyn Geirionydd | Llyn Cwm-y-ffynnon | Llyn Cerrig Bach | Llyn Arenig Fawr | Llyn Alwen | Llŷn | Craig y Llyn | Alwen Reservoir |