Trail Running > Routes > Brecon Beacons Routes > Fan Fawr Four Peaks
A 20 km mountain circuit across the quiet uplands of Fforest Fawr, linking four summits with wild moorland and ancient tracks.
–Route Link-Up– This route forms part of the Fforest Fawr Round – a 38 km mountain run offering one of the most comprehensive tours of the Fforest Fawr uplands in a single, continuous circuit. View Route
Why run this trail?
The broad uplands of Fforest Fawr may lack the dramatic escarpments of neighbouring Corn Du and Pen y Fan, but they offer something altogether different: lonely valleys, rolling moorland and summits that see remarkably few visitors.
This high-level circuit starts beside the beautiful Afon Llia and links the quiet peaks of Fan Llia, Fan Dringarth, Fan Fawr and Craig Cerrig Gleisiad, before returning via the ancient Sarn Helen Roman road.
Despite its wide grassy ridges, this isn’t just a straightforward circuit of summits. The traverse across the upper Dringarth valley crosses wild moorland and boggy ground, with several stream crossings and a genuine sense of remoteness. The effort is rewarded on the climb to Fan Fawr, where sweeping views open out across Ystradfellte Reservoir, the Central Brecon Beacons and the surrounding peaks.
The return leg provides a welcome change of scenery, where the colourful cliffs and the hanging valley of Craig Cwm Du contrast nicely with the open moors, framing fine views of Fan Gyhirych and the Black Mountain.
If you’re looking to escape the crowds and experience one of the Brecon Beacons’ quieter mountain landscapes, Fforest Fawr is hard to beat.
Sarn Helen Car Park to Fan Llia
From the car park, take the bridge across the river and follow the track immediately off to the left. It quickly curves right and heads up a steep bank following the line of a fence and broken wall.
Ignore the first stile and keep climbing for a further 400 m until you reach the brow of the hill and then cross over the stile on your left. You’ll see the high ground of Fan Llia immediately up ahead. Follow the grassy track for 2 km as it curves and ascends steadily to join the Beacons Way up to the summit.
The climb provides a decent warm-up, averaging out at about 10%. The really good news is that you’ve already banked nearly a third of the day’s total ascent by the time you reach the top of the first peak.
A stone cairn marks the top of Fan Llia (632 m) where you can enjoy views of Fan Nedd to your left and Fan Fawr on your right, each mountain prominent in their adjacent valleys.
Fan Llia to Fan Dringarth
The clear onward track from Fan Llia offers a change of pace – a nice flat kilometre to reach the subsidiary peak of Fan Dringarth (617 m). You’ll see views down over Ystradfellte reservoir start to open out to your right, dominated by the rump of Fan Fawr at the head of the valley.
The eastern side of Fan Dringarth’s summit offers some textural variation caused by historic landslips – a quilt of hollows and exposed scars of rock in an otherwise smooth-as-felt landscape.
Fan Dringarth to Nant y Gaseg
Stay on the Beacons Way to head north from Fan Dringarth along the top of the ridge, enjoying great views of Fan Frynych, Craig Cerrig Gleisiad, Pen y Fan and Corn Du.
After about 800 m, keep your eyes peeled for a right turn off the main track headed down into Cwm Dringarth – an almost invisible track that can easily be missed, despite it being part of the Cambrian Way.
A brief pathless section ensues and you’ll need to pick your way around some bogs and a small stream before hopping on to some more promising trods. These soon resolve into a groove of singletrack that drops quickly down to Nant y Gaseg.
As you descend, look across the valley – in good visibility, you’ll see the onward trail to Fan Fawr as a dark ribbon in the grass, snaking its way up the mountainside opposite.
Nant y Gaseg to Nant Mawr
There’s a convenient bed of sandstone to cross Nant y Gaseg and, just beyond the stream, the track skirts a small cascade framed nicely by a view back up to the ridge you just traversed. After a summer of extended heatwaves, however, the cascade was a little underwhelming when I ran it.
Follow the undulating track as it curves southeast around the head of the valley for about 1 km, crossing Nant y Gwair and Nant Mawr before the climb to Fan Fawr begins.
As a whole, these three stream crossings are straightforward in dry conditions. After prolonged rain or during winter, however, higher water levels and boggy ground would make this a different proposition.
Nant Mawr to Fan Fawr
The climb up to the summit of Fan Fawr is steep but the surface is fairly kind – compacted earth and grass that’s hardly eroded at all. It’s the biggest climb of the day at just over a kilometre and averages out at about 18%, so it’s a bit of a grind.
If you need a tactical pause, the views are first rate. Looking back, Fan Nedd, Fan Gyhirych and the Black Mountain escarpment stretch away behind you. To the north, the upper fringes of Fforest Fawr – Craig Cerrig Gleisiad and Fan Frynych – frame the skyline, while ahead Corn Du and the Central Beacons finally come into full view.
Fan Fawr Summit
The top of Fan Fawr (734 m) is marked by a modest cairn that looks like it sits in a pool of water for a good part of its existence. Nevertheless, the views across to the Central Beacons now deserve your full attention: the distinctive profile of Corn Du holding court above the thin tract of the A470 and The Storey Arms hugging the valley floor below.
If you want to tag on a visit to Fan Fawr’s trig point (slightly lower at 715 m), head southwest from the cairn for about 700 m. With over half the run still ahead of me, I skipped it and cracked on.
Fan Fawr Summit to Craig y Fro
This route takes the most direct path off the top of Fan Fawr, plunging straight down its steep north-eastern corner. The path is quite eroded so extra care would be needed when it’s wet and muddy.
At the foot of the descent, bear hard left and then right shortly afterwards where the track splits to cross some tussocky ground with superb views back up to Fan Fawr.
The track becomes a narrow singletrack that hugs the picturesque cascades of Nant y Gerdinen for about 200 m before joining Craig y Fro.
Craig y Fro to Craig Cerrig Gleisiad
The disused quarry site of Craig y Fro blends so seamlessly into the surrounding hillside that it could easily be mistaken for a natural rocky edge. A narrow track threads beneath small rock overhangs high above the valley floor, with fine views across to the Central Brecon Beacons.
Navigation is simple, just follow the winding path around the rim of the mountainside until it pulls away from the edge and starts to climb again. You’ll soon arrive at the top of Craig Cerrig Gleisiad.
Craig Cerrig Gleisiad to Sarn Helen Roman road
An eroded section of track now follows the fence line along the rim of Craig Cerrig Gleisiad. Look over the fence and broken wall to snatch glimpses of the dramatic glacial cliffs, rich with colourful flora. This protected mountain habitat is one of the most beautiful locations in the Brecon Beacons and makes a fantastic trail run in its own right.
Continue around the rim of Craig Cerrig Gleisiad until the path curves north and descends to a fence. Don’t cross the stile. Instead, turn right and follow the fence for about 2 km along the top of Craig Cwm-du, enjoying magnificent views of the colourful cliffs below and the unmistakable profile of Fan Gyhirych beyond.
The track then curves to the right and drops quite suddenly on a steep, grassy bank that may require a bit of zig-zagging to stay upright if it’s wet.
Turn left at the bottom to join the Sarn Helen Roman road.
Sarn Helen Roman road to the Car Park
If you’re looking forward to an easy home straight, Sarn Helen may disappoint: large, loosely packed stones are a constant test underfoot. Sections of this track can also carry a lot of water during winter.
Yet again, the scenery saves the day. Small streams and cascades offer the chance for a freshen up, while the broad outline of Fan Nedd provides a visual anchor for the descent back towards Afon Llia.
After three somewhat rattling kilometres on Sarn Helen, you’ll join a tarmac lane and turn left, heading south down the valley for the final 2 km back to the car park.
Lulled by the rhythm of the river beside me, and pulled along by the outline of Fan Llia and Fan Dringarth now following it directly above, I reflected on another fine running adventure and toyed with a playful epilogue. How about… I’m definitely a Fan of the Fab Fawr? Perfect.
Trail run highlights
Trail run tips
Help improve this guide
Have you run this route? If you’ve discovered a better variation, noticed something that’s changed or have local knowledge to share, I’d love to hear from you.
More trail running routes in the Brecon Beacons
Trail Running Routes in the Brecon Beacons
Disclaimer
All routes and GPX files are provided as a guide only. Conditions, rights of way, and landmarks may change. Always carry an up‑to‑date map and use your own judgement. See the Trail Run Disclaimer page for details.