#261 – Cwmorthin and the mountains of the Moelwynion (Moelwyns)

Llyn Cwmorthin above Tanygrisiau

(Left click images to zoom in, use browser return arrow to go back)

It was a Team training night, and several of us drifted down to the pub afterwards.  The chat is always varied, but I overheard ‘Gaz’ talking about the worlds biggest and deepest slate mine, with miles of passages and hundreds of chambers.   It looked like a trip out that way would fill in a day nicely, which is why Chris and I, plus Border Collie ‘Mist’, were at Tanygrisiau on a fine May morning in 2018.

Setting out from Tanygrisiau

The route

Blaenau Ffestiniog and Tanygrisiau

Blaenau Ffestiniog is well known as being a town that was literally built on the slate quarrying industry, but the huge slate spoil heaps above ground are insignificant compared with the vast underground slate mines in the area.   Amongst the most famous of these is the complex of mines and tunnels of Cwmorthin and Rhosydd, just above Tanygrisiau.

Llyn Cwmorthin and some of the surface works of the slate mine

The ‘barracks’ where slate miners would live during the week

Heading on past Llyn Cwmorthin ….

…. but too slow for Border Collie ‘Mist’

Mining started at Cwmorthin in 1810, but by the 1880’s a series of roof collapses combined with disputes with other mining companies, made the site less viable.   Mining continued though, and tunnels on five different floors were dug below the level of the lake (Llyn Cwmorthin) but when the original company went out of business, the neighbouring Oakeley mining company bought Cwmorthin mine and allowed it to flood to protect their own business interests.

Remains of the chapel ….

…. and the manager’s house, Plas Cwmorthin

Ruined buildings from the quarry workings

Cascades on Allt y Ceffylau

Between the two World Wars, the flooded passages were pumped out to allow mining to resume, but the mine was abandoned during WW2, with only the pumps working to keep the water at bay.  Mining operations were finally halted in 1970 and the works abandoned.  It is possible to visit the underground passages by contacting the Friends of Cwmorthin Slate Quarry, but for most visitors, the abandoned chapel and former manager’s house of Plas Cwmorthin are the most accessible relics.

Start of the track to the upper quarry

Looking back down the cwm towards the lake

Nearly there at the upper quarry

Just a small part of the extensive remains

Flooded mine entrance

At the head of the valley of Cwmorthin, an old quarry track leads to the upper quarry, and just as the visitor becomes used to the scale of the workings at lake level, a whole new complex of abandoned quarry workings comes into view.   Over the many decades, the old waste tips have blended in to become a part of the mountains and are a testament to the hard men who worked here.

Heading up to Rhosydd Quarry

Continuing upwards….

…. with ‘Mist’ ahead as always

The ruins at Rhosydd quarry with Cnicht in the background

At the upper quarry level, an incline carries on gaining height to Rhosydd quarry, with most of the workings here being above ground on what was the ninth level of the workings.    At last we had views of the surrounding mountains, including Cnicht, known as the ‘Welsh Matterhorn’ due to its ‘pointy’ nature viewed from the southwest, and Moelwyn Mawr with Moelwyn Bach beyond, and Rhosydd made an ideal place to stop for a bite and a drink.

Heading towards Bwlch Stwlan below Moelwyn Mawr

The track clinging to the eastern flank of Moelwyn Mawr ….

…. with a steep drop-off to Llyn Stwlan coming up!

From the upper level of Rhosydd, we carried on towards the pass of Bwlch Stwlan, with what should have been a straightforward track running along the eastern flank of Moelwyn Mawr.   For most of the way the track is as wide and as flat as a town pavement, but the weather and seasons have caused the occasional landslip – this might not have been a problem had there not been a steep drop-off to the lake below, and for a short while, Chris was not a happy bunny!

Chris, happy to be off the narrow path ….

…. and heading down to Llyn Stwlan

The dam at Llyn Stwlan ….

…. with a final view of Moelwyn Mawr

Eventually it was possible to escape the narrow path to head down to the lake of Lynn Stwlan, which like so many Welsh lakes is a reservoir.   Despite the hard outline of the dam, the lake looks at home here and part of the mountain scenery.   The dam also makes a handy bridge, leading to an even handier service road running down to Tanygrisiau, and it was a straightforward yomp back to the waiting car, and for ‘Mist’ the ride home for a long-overdue dinner time!

Time to head for home

Text and images © Paul Shorrock

p.s.  Our Scottish trips and bothy walks have taken over the blog  for several months now, so it’s nice to be back on home ground in North Wales with this post

About Paul Shorrock

I've been mucking about in the mountains for longer than I care to mention. I started out by walking my local hills, then went on to rock climbing, mountaineering and skiing. Still doing it, and still getting a buzz. I'm now sharing the fun, through my guided walking business (Hillcraft Guided Walking) and by writing routes for other publishers, mainly Walking World and Discovery Walking Guides. Just to make sure I keep really busy, I am also currently a member of my local mountain rescue team.
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4 Responses to #261 – Cwmorthin and the mountains of the Moelwynion (Moelwyns)

  1. Looks an interesting walk around the quarries – I’ve visited some bits and would love to see around the tunnels some time – I’d also like to try your scary path! I’m not sure how you managed to stay off the 3 hills though and walk beneath them – I’d have been going mad!

    The only black eye I ever got was in those mines. I’d found a sharp piece of slate and decided to use it as a scythe against the huge thistles just to test its sharpness… One thistle won! It bounced back from the slate instead of just slicing through like its mates did and hit me full in the eye. Richard had to pick spines out of my eyeball and my eyelid and it went beautifully deep purple – just in time for me to go back to work. That caused some comment I can tell ya!


  2. The path isn’t all that scary, but Chris didn’t enjoy it, that’s for sure – you could include it with a round of the tops.

    Nasty accident with the thistle! More scary than the scary path!


  3. rlbwilson says:

    That’s a place I have been and intend to go back to, for a bit of industrial photography. I’ve also been down the mines with a led school party (too much snow around for our climbing session, and a bit cold for canoeing) – absolutely amazing experience!


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