The lonely lake Llyn Cwmystradllyn lies in a basin between the wild mountains Moel Hebog and Moel-ddu. Above it is an old quarry, and the slate mill alongside the lane was powered by the lake`s outflow. A dam was built in 1960 and the lake now provides drinking water for the Lleyn peninsula. It is a popular fishing venue and permits are available in Porthmadog. There are interesting, scenic walks in the area and the lake can be reached by a lane off the A487 between Porthmadog and Caernarfon.
