Trail Running > Routes > Brecon Beacons Routes > Usk Reservoir Circuit
A peaceful 12 km circuit around Usk Reservoir and Mynydd Myddfai, with forest trails, open moorland and stunning views.
Why run this trail?
Tucked away in the western corner of the Brecon Beacons National Park, Usk Reservoir is one of the area’s quieter gems. Surrounded by forests and rolling moorland, it remains refreshingly free from crowds despite offering some of the finest scenery in the western Beacons.
The route starts from what must be the region’s most beautifully situated car park, with uninterrupted views of the Black Mountain escarpment (Mynydd Du) providing an inspiring backdrop from the outset. It’s a wonderful place to begin and end the run, whether you’re cooling your feet in the river afterwards or simply lingering with a picnic.
Once you hit the trail, well-surfaced forest tracks make for relaxed, uncomplicated running above the shores of the reservoir. The route then climbs gently onto the open moorland of Mynydd Myddfai, providing 360-degree views of the entire Brecon Beacons, the Cambrian Mountains and deep into Mid Wales.
There’s a tranquil feel to the whole route. It offers just enough wild mountain scenery to feel like a genuine escape, while remaining easy to navigate and highly runnable throughout. Whether you’re looking for a gentle recovery run, a confidence-building day in the hills or just a peaceful morning in nature, it’s difficult to think of a better choice.
Glasfynydd Forest Car Park to Usk Reservoir
Once you’ve kitted up and admired the scenery, head out of the car park, cross the lane and pass through the vehicle gate directly ahead. You’re on a forestry service track that descends very gradually for the first 500 m or so – a gentle start to proceedings.
The track then climbs gradually and curves around the tail end of the reservoir, offering intermittent views of the water to your right. On your left, you’ll see the smooth, rolling hills appearing over the tops of the trees.
After a couple of kilometres, just on the apex of a bend in the track, pass over a stile on your left onto moorland.
Usk Reservoir to Pen Caenewydd
Follow the path across a short boggy section through dense rushes. The path is a little faint at first, but it’s easy to aim for the visible track ahead as it starts to ascend up the hillside.
The climb to the top of the grassy ridge of Pen Caenewydd (429 m) is perfectly pitched, averaging out at about 7% over 1.5 km. Navigation is simple too – aim high and keep right where the track splits in a couple of places. The only reason you’ll be tempted to stop is to take in the unbeatable views of the Black Mountain unfolding behind you. This has to be the most dramatic and all-encompassing view of the ridge offered anywhere in the National Park.
You’ll soon arrive at a small stone pillar at the top of the hill, to be greeted by a sweeping view of the Cambrian Mountains beyond.
Pen Caenewydd to Mynydd Myddfai
The clear onward track towards the higher mound of Mynydd Myddfai perfectly captures the character of the route: uncomplicated running in magnificent surroundings, leaving you free to soak up the scenery.
To your left, extensive rolling views open out across Mid Wales, while to your right the entire scope of the Brecon Beacons is laid out like a Toposcope – from the Black Mountains on the eastern fringes of the region to the western reaches of Mynydd Du.
The views from such a modest hill really are quite staggering and I found myself stopping to identify the various peaks through the summer haze – a kind of impromptu identity parade of mountain summits.
It’s an easy, undulating run along the ridge for just over a kilometre to reach the trig point on Mynydd Myddfai.
Mynydd Myddfai to Glasfynydd Forest
I wish I could comment on the trig point on Mynydd Myddfai (440 m) but my visit was curtailed by an extremely enthusiastic swarm of wasps that seemed to have developed an unhealthy interest in sweaty running gear. Remembering that discretion is the better part of valour, I decided a tactical retreat was the wiser option on this occasion.
It’s a gentle descent from the top of Mynydd Myddfai – the track drops down into a small hollow and becomes stony again before fording a small stream at Pant y Ddwyros. From here it’s a short onward leg to the drystone wall that marks the northern perimeter of the forest.
Glasfynydd Forest to Usk Reservoir
Pass through the gate into Glasfynydd Forest and continue straight ahead on the track, skirting a cleared area of plantation to your right. Bear left where the track splits, joining the main service track as it winds through the forest.
After about 750 m, you’ll arrive at a small clearing, with views of the water becoming apparent through the foliage. Stay on the main track heading roughly southeast until you reach a t-juntion on the banks of the reservoir. Turn left and make your way along the lane, which becomes tarmac as you approach the dam wall at the head of the reservoir.
Usk Reservoir to Glasfynydd Forest Car Park
Cross the dam wall on the footpath/service lane and once you reach the far shore, turn right by the main reservoir car park.
The next kilometre ascends very gradually on the metalled lane until you reach an access track back into the forest on the right. Pass through the vehicle barrier and continue on the forestry track for 400 m until you reach a prominent junction of tracks, with views down to the water. Stay on the main track as it curves left and follow it all the way, ignoring any offshoots until you reach a t-junction after about 800 m.
Turn left at this junction – you may recognise this track as the one you set out on at the beginning of the run. After 300 m, you’ll be back at the car park with another beautiful Brecon Beacons trail run in the memory bank.
Before you leave, it’s worth strolling out to cross the bridge over the River Usk, where you can cross the county line into Carmarthenshire and pause for one last look at that magnetic view of the escarpment of the Black Mountain.
While there are no refreshment options close at hand, I thoroughly recommend the excellent International Welsh Rarebit Centre in the nearby village of Defynnog. Cheesy goodness and Welsh heritage in every bite – a fitting end to one of the Brecon Beacons’ most relaxing trail runs.
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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.