The Carmarthenshire Fans (Bannau Sir Gaer) are located in the Black Mountain range of the Brecon Beacons. Whilst often overlooked in favour of the taller peaks to the east, they are no less impressive. Though popular with locals, this range is less accessible than others and remains relatively quiet year-round. The range's highest point, Fan Brycheiniog, is 802m above sea level and the majority of the route is often snowbound in the winter months.
This round trip begins and ends at the Llyn y Fan Fach car park (SN 79977 23824) and ascends southward to Llyn y Fan Fach via the Beacons Way.
The route turns westward, continuing its ascent via a footpath to rejoin the Beacons Way on the Bannau Sir Gaer ridge.
Taking the Beacons Way northeast along the ridge, the route summits Picws Du (SN 81173 21862) and Fan Foel (SN 82148 22354) before turning southeast to summit Fan Brycheiniog (SN 82528 21799), the tallest of the Carmarthenshire Fans.
Descending Fan Brycheiniog, the route deviates from the Beacons Way, turning eastward down a footpath to the southern tip of Llyn y Fan Fawr, where the route rejoins the Beacons Way.
Hugging the eastern bank of Llyn y Fan Fawr, the route follows the Beacons Way northwest, southwest, then westward, along the foot of the Bannau Sir Gaer ridge.
The route closes the loop at the northern tip tip of Llyn y Fan Fach, before turning northward to descend via the Beacons Way and return to the starting point at the Llyn y Fan Fach car park (SN 79977 23824).