This mountain lake is situated within the Carneddau range in Snowdonia. The lake has an area of approximately 6 acres, is 250 metres long and is overshadowed by the peaks of Pen yr Ole Wen (the seventh highest peak in Wales (3209 feet)) and Carnedd Dafydd (the third highest peak in Wales (3425 feet)).
The remains of two WWII aircraft can be found on the steep slopes around the lake, which crashed in 1942 and 1943 respectively. The outflow of the lake, Afon Lloer runs down into Llyn Ogwen beside the A5. The English translation of Ffynnon Lloer is ‘Well of the Moon’ or ‘Source of the Moon’ and an old superstition says that ‘you must see the Moon in the lake once a month’. This saying seems confusing, so there may have been something lost in translation over the years.