Llyn y Fan Fach of the Lady of the lake in Welsh and English. Llyn y Fan Fach Llyn y Fan Fach (Welsh meaning "Lake of the small hill") is a lake of approximately 10 hectares on the northern margin of the Black Mountain in Carmarthenshire, South Wales and lying within the Brecon Beacons National Park. The lake lies at an altitude of approximately , immediately to the north of the ridge of the Carmarthen Fans. It is the smaller of two lakes within this mountain massif: the slightly larger Llyn y Fan Fawr is about to the east. The lake is overlooked by
Pen-y-Gwryd Plas y Brenin. The Old Miners' Track from the Snowdon copper mines are now part of the modern A4086 road between Pen-y-Gwryd and Pen-y-Pass. It continues northwards beyond Pen-y-Gwryd skirting Glyder Fach to Bwlch Tryfan and Dyffryn Ogwen. From Pen-y-Pass is the "PYG track", one of the many routes leading to the summit of Snowdon, its name is believed be derived from the initials ("P-y-G"). However, older maps show it as the "Pig track", a name derived from "Bwlch y Moch" (the Pigs' Gap). During Roman Britain, the Roman Army built a marching camp at the head of Dyffryn Mymbyr