Trail Running > Routes > Snowdonia Routes > Cnicht & the Moelwyns
A classic 14 km Snowdonia mountain run linking Cnicht, Rhosydd Quarry and the summits of Moelwyn Mawr and Moelwyn Bach.
Why run this trail?
Known informally as the “Welsh Matterhorn”, the rocky pyramid of Cnicht dominates the skyline of the southern Moelwynion and instantly begs to be explored.
This classic Snowdonia fell-running circuit links Cnicht with the summits of Moelwyn Mawr and Moelwyn Bach via the atmospheric ruins of Rhosydd Quarry, perched high above the valley of Cwmorthin. The result is a spectacular mountain journey through some of Eryri’s most dramatic and less-frequented terrain.
While the distance and elevation gain are modest by Snowdonia standards – Moelwyn Mawr marks the high point at 770 m – this is a serious mountain outing. Expect steep, broken ground, pathless sections of open fell and several engaging scrambles, both up and down.
It doesn’t make for the fastest running, but that’s what makes it special. This is a route to savour: expansive views of mountains and coastline, a real sense of exploration and some of the finest running in Snowdonia. Once beyond the summit of Cnicht, the sense of remoteness only grows, leaving you with the memory of a wild and beautiful circuit that lingers long after the finish.
Croesor to Cnicht
The run starts from the small car park in the former mining village of Croesor. To reach it, follow signs for Plas Brondanw Gardens from the A4085 just north of Garreg, then continue for two miles on a narrow single-track lane into the valley. The car park accommodates around 20 vehicles and has a donation box and portaloo.
Turn right out of the car park and climb through the village on the lane and then through woodland on a wide, stony track. Follow signs for Cnicht – the track bears to the right across the moor. You’ll see the top of Cnicht (or at least the first false summit) almost instantly and the path is obvious to follow.
As you climb, views across to Moel Hebog, the Nantlle Ridge and the major peaks of Snowdonia open out to your left. It’s also worth taking a look back for views of the coast at Porthmadog if you need a crafty breather!
The track steepens and becomes narrower as it winds through a series of rocky knolls, each one acting as a false summit. The path fragments in places and progress becomes more hands-on, with several short scrambles where running is neither practical nor advisable.
None of it is particularly exposed, but it does afford some dramatic views down into Cwm Croesor and the Moelwyns standing sentinel above it.
After just 3 km and 550 m of climbing from the car park, you’ll arrive at the small summit cairn of Cnicht (689 m). If you’re blessed with a clear day, the 360-degree views are fantastic and even if you’re not you should still glimpse your next peak – Moelwyn Mawr – breaking through the clouds across the valley.
Cnicht to Rhosydd Quarry
It’s a short hop on grassy terrain across to Cnicht North Top (688 m). From here, the series of small lakes that dot the undulating plateau become apparent and the trail broadens out, descending in the general direction of Llyn yr Adar. At the junction of tracks, bear right across rough moorland towards the slate spoil heaps of Rhosydd Quarry, which will now be clearly visible in the distance.
While the quarry workings themselves are easily identifiable, the trail here is less so – it fragments and becomes indistinct and very boggy. Pass through the fence at the first gate to skirt the western shore of Llyn Cwm Corsiog and pick your way down to Rhosydd Quarry.
Rhosydd Quarry to Moelwyn Mawr
As post-industrial landscapes go, the scale of the abandoned works at Rhosydd Quarry are impressive – the spectral remains of barracks, workings and rusted machinery are dwarfed by huge spoils of slate amidst a natural amphitheatre of crags and mountains. It’s an atmospheric place and I found myself exploring some of the larger structures while gathering myself for the drag up to Moelwyn Mawr.
The trail then climbs out of the quarry site via a prominent slate incline – the remaining bed of a cable pulley system that rises steeply out of the bowl – to emerge onto a grassy expanse with the hulk of Moelwyn Mawr towering ahead.
Keep to the right side of the fence – ignoring the signpost (green arrow) off to the left – and continue on the steep track up and around the shoulder of the mountain. It’s a tough slog up to the top, but notably easier underfoot than some of the rocky terrain that preceded it.
Thick cloud and hailstones had descended with a vengeance as I tapped the summit cairn of Moelwyn Mawr (770 m), so I can’t personally attest to the (reportedly) great views from the top. With no reason to loiter, I retraced my steps briefly then continued down the southern slope of the mountain towards the craggy ridge of Craigysgafn.
Moelwyn Mawr to Craigysgafn
The ridge of Craigysgafn is a series of steep, rocky knolls that requires a bit of careful scrambling – especially in the wet. The ridge offers bird’s-eye views of the Llyn Stwlan Dam and hydroelectric station below and expansive views across to Blaenau Ffestiniog.
The impressively craggy north face of Moelwyn Bach looms ahead as you descend sharply into a small saddle to begin the final climb of the day.
Craigysgafn to Moelwyn Bach
The climb up to Moelwyn Bach is a short, steep kick up around the shoulder of the mountain that feels mercifully short for tired legs.
The top is marked by a rocky cairn, with great views over southern Snowdonia and a sweeping view of the coast at Porthmadog and further towards the Llŷn Peninsula.
With the final climb in the bag, it really is downhill all the way from here.
Moelwyn Bach to Croesor
There’s a clear, inviting grass track along the broad ridge of Moelwyn Bach all the way down to Croesor. It’s a fast, hassle-free descent that feels good after all that uphill effort and careful traversing of crags.
The path briefly joins a forest track before emerging onto a small lane down to Croesor for the final short stretch on tarmac back to the car park.
Looking up from the lane, the entire circuit was laid out in profile above the valley – Cnicht, Moelwyn Mawr, Craigysgafn and Moelwyn Bach – dappled with sunlight. After all the scrambling, navigation and quiet mountain miles, it felt like a fitting final scene to an unforgettable run.
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