The highest of the Ogwen Valley AA waters at six hundred and seventy-eight metres — a tiny Carneddau cwm lake, two hundred and fifty by a hundred and fifty metres, in the cwm beneath Pen yr Ole Wen and Carnedd Dafydd. Excellent wild brown trout to a pound on a water you can walk round in twenty minutes if you don't fish it. Traditional fly only, no bubble float. Forty-five to sixty minutes' walk in from the road.
- Lake
- Ordovician volcanics sediment