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Cefn Du – Trail Run and be Dammed

By Dave Roberts   

on July 4, 2015    No ratings yet.

Cefn Du – Trail Run and be Dammed

Further Details

Route Summary:

Route Start Location:

5.07 km 146 m

Calculate the time using Naismith’s Rule and factor in your own pace.

Activivity Type: 

Summits and Places on this Route


Check out the businesses nearby for more places to stay and drink.


Remember that we cannot outline every single hazard on a walk – it’s up to you to be safe and competent. Read up on Mountain Safety , Navigation and what equipment you’ll need.

Parking :

Public Transport:

Traveline for UK Public Transport

Recommended Maps


Cefn Du – Trail Run and be Dammed Ordnance Survey Map and GPX File Download

Download file for GPS

Cefn Du – Trail Run and be Dammed

Finding new trail runs that don’t turn into fell runs is more of a challenge around these parts than the run itself. So it was a pleasant surprise to explore new paths on what was going to be a fairly standard easy run up to the minor and far from salubrious brick-strewn summit of Cefn Du. While this moorland doesn’t allow for the longer runs over the Uwchgwyrfai Common on the other side of the valley, it’s still good for shorter runs and the views are just as good.

The future of this area is uncertain as there are plans to develop a hydro-scheme in the old quarries, but access during the work and after will probably be affected. Very little info is available on the official site other than footpath may be temporarily shut / permanently diverted- Glyn Rhonwy Hydro Scheme – or if it is then it’s well hidden in the jargon and the use of poorly detailed maps. If in doubt, visit this site as they should have to notify of any closures of a public road and common land.


1 Start the run from the Bwlch y Groes carpark. The approach road has become particularly uneven over the last few years, so you will need to take care (or start from Waunfawr for a slightly longer run).  Follow the track at the end of the carpark that contours above the main track to the bwlch. You can take either route if you do miss the path!


2 Continue to the boundary wall at the bwlch and take the now rather clear track – following the preliminary pumped-storage work presumably –  up to your left along the boundary.


3 The track turns 90deg left at the first quarry (fenced off, so you shouldn’t run into it unless you’re some sort of fell running hurdler)and climbs onto the moor.


4 You can follow the fence if mist makes visibility poor, otherwise head right along a faint path towards the higher ground. This brings you to the brick-strewn summit of Cefn-du. Hardly significant on any list at 441m and not enough re-ascent between it and Moel Eilio, but a fine viewpoint nevertheless. All the bricks are remains of Marconi’s radio transmitter (links to a walking route with some more info on this).



5 Follow the fence (left as you approach from the route, or roughly south) which has a clear path down hill that then turns sharp right with the fence. You can follow a good path along the fence before it heads towards a minor top (marked with a cairn) at SH538 602. Don’t get tempted to head directly towards it from the fence as the area directly in between is a morass! The path winds around, it’s next steps hidden by the terrain until the cairn’s reached.


This minor top doesn’t even merit a mention on the map, or even a ring contour, but as we descended to the track it revealed most surprising view south as far as the Rhinogydd and even Gau Graig on Cadair Idris! That was of course after looking at them in disbelief for around ten minutes thinking that this was an impossible view from this far north! This really made our run tonight.


6 The path continues both NW and SW, and we took the latter path leading to an enclosure and clear track at SH535 600. Turn left at this track and the minor road is surprisingly close. Despite the feeling of isolation, with the great and the good of Snowdonia’s summits as a backdrop, you’re rarely further than a few 100m from the road!


7 Finally follow the minor road for a punishing final 1.5km back to the start.

Dave Roberts founded Walk Eryri in 2004, with the aim of providing routes that are off the beaten track. Walk Eryri is now part of Mud and Routes which continues to provide more off beat routes and walks in Snowdonia and beyond. Dave has been exploring the hills of Eryri for over thirty years, and is a qualified Mountain Leader. Dave also established Walk up Snowdon, Walk up Scafell Pike and Walk up Ben Nevis just to mention a few.
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