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Cefn Du and Moel Smytho from Llanberis

By Dave Roberts   

on September 3, 2014    5/5 (1)

Cefn Du and Moel Smytho from Llanberis

Route Essentials

Route Summary

See the end of the article for local information about parking, public transport facilities, pubs and cafes.


15.07 km


517 m


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

Start Location


Moderate Walk


Weather Forecast:

Met Office Snowdonia Mountain Weather

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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. 

Cefn Du and Moel Smytho from Llanberis Ordnance Survey Map and GPX File Download

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Cefn Du and Moel Smytho from Llanberis

I had decided to go up today, no matter what. Rain, sun, cloud, whatever.

Thing is, you see, I wanted to test a GPS system out. To start with, I’m sure not many people are familiar with the top of Cefn Du. For those people, it is a heathery, boggy moor that separates Llanberis from Waunfawr, in front of Moel Eilio.

Route finding can be difficult due to many tracks, and importantly, because the path follows the edge of an open slate quarry at one point. So bear this in mind.

OS Map Required Explorer 017BMC MapLandranger 115

The route starts, near my sister’s house and had to use my willpower to refuse the hospitality of a large mug of coffee. I knew it would only take a mugful and I’d stay indoors all day. As it were, I ascended the path to the waterfall (for those who don’t know my sister, you get to the path by following the road to the Snowdon path and turning right underneath the Railway Viaduct. The path up to the waterfall is just past this on your left, parked by a sign. It is a tarmacked track with a cattle grid and kissing gate at its base.)


This track quickly takes you up to the bridleway (SH 572 590) at the base of Cwm Dwythwch where you turn right. If you look at my GPS log, i followed a track to the bridleway that left me a little further east. I was contemplating ascending this track to Snowdon Ranger (other side of mountain), but decided to follow original track.

The track is now easy to follow all the way to Bwlch Y Groes. Initially the bridleway is over rough ground, before you pass a derelict house and follow the (now a) track along the wall. The footbridge shown below is no longer there as it was washed away a few years ago! You know you are in Bwlch Y Groes as you can see the plantation and quarries, and a path leading left up Moel Eilio. I headed right, up through the quarries, being a little difficult to follow in parts, arriving at the chasm of the disused quarry as intended. Looking at the map afterwards i realise i went ahead rather than left (ironically after first going left for and thought my GPS said i was wrong. That’s one for Instinct over GPS).


This is an area that would be of interest to industrial archaeologists. I have no pictures as it had just started raining heavily, rather than showers, and was too much for my Montane pertex top. Time to change into full waterproofs. A point here is that had I bothered to use my 1:25000 map for this part of navigation, I would not have become slightly lost. The field boundaries on those maps are the ideal handrails to follow along this part of the route.


From the quarry, you carry on keping it to your left until you come to a wall and a metal ladder stile. Cross this and then a track appears to your right that takes you all the way to the summit of Cefn Du. It is a barren, windswept moorland that was the site of the first radio transmission from the UK to Australia in 1918, Marconi used the hill to experiment with long distance radio waves, the station itself now marked as climbing centre on our maps, and the summit having remains of the antennae buildings. I used the summit stop for a quick coffee, and a text message home to say i was OK.


It was a quick coffee, the rain and wind was too much and I descended SE along the wall and the path that is there on the ground (but not the map). This is the only place I encountered drifts of snow, where snow was knee deep. The track is narrow, but straightforward, and once at the track is again easy to follow downhill.

DSC_0234 DSC_0236

The next section into Waenfawr itself is more complex. I have never liked lowland paths, too many gates, fields, stiles and mud. A short distance along the road you reach a side road (SH 353 598) that takes you past some houses and then down over the fields. Follow the signs for Four Valley Way and they should take you down to the pub (Snowdonia Park – SH 526 588) in Waenfawr. If you want a short day, you can finish here, perhaps get the train into Caernarfon.

I couldn’t go in for a pint during this walk as I was too muddy, but they do have an excellent microbrewery there. Seriously though, I have tried a pint before and it is good, and they are in the CAMRA pub guide.

As I couldn’t slip into the pub and waste the rest of the afternoon, I had to finish the walk off. Just further down the road, there is a road junction to the right (signposted – Rhosgadfan 2), you follow this and you shortly come to a signpost (Y Fron 31/2 miles) that indicates the path onto Moel Smytho. It is a steep slog through the trees, and beware the metal ladder stiles put in to aid the climbing of some rocky sections, one felt loose.


Once up on the moor, the track is difficult to follow, and I think a better line is to follow the path up and over Moel Smytho, not the path that skirts it to the west. However, once you reach the plantation the path becomes wider and is quite clear for a few kilometres to the base of Mynydd Mawr. Personally, I had to descend as I had a date in a pub with a Rugby match, and found the road at Penyffridd and down to the Main road (fair old boring walk, and I swear I’ll NEVER descend this way again! Much better would be to follow the track around to Penygroes. This would have been a similar distance, but better and safer.)


As far as this walk goes, its purpose was to get into the snowy hills but not onto the snow as I lack the equipment (and probably practice) for these conditions. I also thought this was a different route to follow, and toyed with the idea that a similar route is very unlikely noted anywhere else. Well I was wrong! Gwynedd County council have a waymarked route (obviously well advertised!) called the Four Valleys Way. This starts in the Ogwen valley, over to Llyn Peris, Waenfawr and finally Penygroes. Click on the links for full details (in PDF format). It is a definite low level option when the weather is poor, and there is still the chance for a view. However I’d modify the route (like this one!) and take in the minor tops that it skirts. Still, I now know that the descent I’ve planned from Mynydd Mawr to Waenfawr to make it a longer day is a decent route.

Local Information and Recommended Maps and Guidebooks

Route Summary:

Route Start Location:

15.07 km 517 m

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

Activivity Type: Moderate Walk

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

Weather Forecast:

Met Office Snowdonia Mountain Weather

Check out our Best Mountain Weather Forecast?

Recommended Maps


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Dave Roberts

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