 The Llyfnant rises at Llyn Penrhaiadr in the Uwch Garreg mountains south of Machynlleth.It flows northwards through mountainous scenery for about three miles, before suddenly coming to the edge of the escarpment and plunging into a ravine in a series of waterfalls and cascades known as Pistyll y Llyn, descending abruptly from .At a more leisurely pace, it now begins to curve gradually towards the west and passes the hamlet of Gellifudr at the end of the first unclassified road it has encountered.