The northern face of Waun Lefrith was home to a glacier during the ice ages which gouged out the cwm in which Llyn y Fan Fach now sits.

[2] Large moraines occur to the east of the summit at the base of the scarp, and below the prominent peak of Picws Du as well as those damming the Lake.

The most popular path of ascent is that from the car park at the foot of the water board road running steeply up to Llyn y Fan Fach and over which lake the mountain looms.

The walk along the escarpment gives excellent aerial views of the lake, although some care is needed in poor visibility or cold weather.

The footpath from Llanddeusant avoids the parallel tarmacked road to the dam, rising along the ridge which leads directly to the summit.

As in all mountains care is needed when the weather is poor, when visibility falls due to mist, fog or driving rain and snow.

The skylark is plentiful due to the extensive rough pasture present below the main peaks which allows ground nesting of the species.