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  • iainthow


Updated: Mar 11

Half a million people a year climb Snowdon, making it one of the world's busiest mountains - while researching my master's thesis on it I counted 3000 people in just one midweek day. Despite this parts of the mountain see few people. Upper Cwm Caregog springs to mind, and Cwm Merch, but there's only one of the six major cwms that doesn't have a path in it, and that's Cwm Glas Mawr. Fortunately for lovers of solitude and wildness it also happens to be the craggiest part of the mountain. Cwm Dyli has Lliwedd and Clogwyn y Garnedd but the north side is basically a scree slope, whereas Cwm Glas Mawr has cliffs everywhere you look. Even getting into either of the upper branches requires winding in and out of rock slabs and squeezing between sizeable faces. It's very much a climber's and scrambler's place, and when you do meet people they invariably seem to know what they are doing and are well equipped, something you can't say on many parts of the mountain.

Crib y Ddysgl and Cwm Glas Mawr, Snowdon

Cwm Glas Mawr and Crib y Ddysgl

A note on names. Although the National Park Authority has recently stopped using Snowdon as a term, replacing it with the Welsh Yr Wyddfa, these aren't really describing the same thing. Yr Wyddfa is the name of the highest peak, meaning "the tomb", and named from the ancient cairn that used to stand on the summit before the engineering works of the last 150 years. Snowdon is the name of the whole range, an ancient name too, first recorded in the Anglo-Saxon chronicle of 1095 and meaning "snowy mountain". It was named either by English sailors looking up from the sea, or possibly dates back to the 7th Century Anglo-Saxon occupation of Anglesey ("Island of the English"). I'm therefore quite happy to continue using the English name for the range as a whole (but have always used Yr Wyddfa for the main summit). Getting more granular, the OS have Cwm Glas Mawr as the more open lower part of the cwm, with the two upper branches being Cwm Glas and Cwm Uchaf, but Cwm Glas Mawr is most often used to mean the whole lot. I'm slightly surprised that the lower part isn't known as Cwm Glas Isaf but maybe I've just been talking to the wrong people. In addition the summit backing the cwm is almost universally known as Crib y Ddysgl these days, but that's a result of a misplacement on OS maps. Strictly speaking the summit is called Carnedd Ugain, with Crib y Ddysgl being the ridge running eastwards from it, the upper continuation of Crib Goch. That horse bolted so long ago though that the stable has now been demolished and replaced by a car park.

Cwm Glas Mawr, Snowdon in winter

The two upper cwms, with Crib Goch and Clogwyn y Person behind

Nomenclatural quibbles over, how about the place itself? It consists of a lower cwm, sloping fairly steeply down to the road, and two much more enclosed upper cwms. The cliffs behind these are both crested by well known scrambles, the tricky Clogwyn y Person Arete and the famed Crib Goch. The latter is easily the most popular scramble in Wales (only the North Ridge of Tryfan comes close), and anyone in Cwm Uchaf at a weekend is treated to a skyline of slowly moving spikelets.

Crib Goch, Snowdon

Crib Goch, quiet late in the evening

Crib Goch is usually approached from Pen y Pass, so feels more like it belongs to Cwm Dyli than Cwm Glas, but the North Ridge makes a fine way onto it too, finishing up the distinctive red screes that give the peak its name. This approach can be made more exciting by starting up Jammed Boulder Gully, probably worth Moderate. It hardly ever dries out completely and climaxes with a set of tricky moves performed in semi-darkness under the eponymous huge boulder. I've done it once and haven't felt the urge to repeat the experience 😬.

Crib Goch Pinnacles, Reade's Route, Snowdon

Crib Goch pinnacles, Reade's Route is the clean central buttress

For climbers the classic way onto Crib Goch is to do Reade's Route on the face below the pinnacles. Back in the days of the ancients this was graded "Exceptionally Severe" but iconoclasts knocked it down to V Diff until recently, when it was (rightly) upgraded again. Krystle and I climbed it at the end of a lovely warm dry autumn (it was November but felt like August). Near the top you climb to a tiny exposed perch on top of a pinnacle and make a mindblowing step across the gulf to the main cliff. It's irreversible and you are reaching for smallish holds on a vertical wall below an overhang so it's tremendously intimidating. At the overhang the holds become much bigger though and a comforting crack takes you to the top of a slightly larger pinnacle. The last pitch is still wildly exposed and no pushover either, so it's quite a finish. We had driven over from the Peak that morning so were quite late and had Crib Goch to ourselves in the sunset, descending Cwm Glas in the semi dark. As good a day out as you could wish for.

Reade's Route, Crib Goch, Snowdon

Looking down to the pinnacles of Reade's Route

I had descended Cwm Glas in the gloaming before, on a day with Rob Ivens when we did nearly 400m of climbing on three different cliffs. We started with a couple of VS routes on Dinas Mot, Lorraine and Western Slabs, the former with a superb second pitch of sustained 4c slab, the latter a return bout after being rained off it a year or so earlier. We then headed up to Main Wall on Cyrn Las, one of the best Severes in the country. Cyrn Las (often Gyrn Las) is another naming mistake incidentally, its Welsh name being Diffwys Ddu ("Black Steep"), Gyrn Las being the ridge to its right. Main Wall winds its way through very steep rock amongst a bunch of harder climbs and as we approached it things got more and more impressive. I was starting to feel quite psyched out when Rob said "I'm glad I'm doing this with someone who knows what they're doing". I couldn't really suggest backing out after that!

Cyrn Las (Gyrn Las), Snowdon

Cyrn Las

Actually it was Rob who led the hardest pitch, an exposed vertical wall where good holds existed, but not where you wanted them. I got the reward, the wonderful 4a slab perched in the air above it. We finished with Gambit on Clogwyn y Ddysgl, then graded V Diff but with 4c moves on three of its four pitches! I led the last one, on rock which was glowing orange in a magical sunset. We came back down the Clogwyn y Person arete in the afterglow and just made it back to the road before it was totally dark. One of my best climbing days ever.

Sunset on Esgair Felen from Cwm Glas Mawr, Snowdon

Sunset on Esgair Felen from the upper cwm

I've had several other encounters with the Clogwyn y Person arete, the most memorable being a solo of the Direct start in walking boots a very long time ago. It was graded Diff then, and at the time I worked on the basis that I could always solo Diffs. It isn't steep but there's a distinct shortage of positive holds, and in the damp conditions it felt very insecure. I have a strong memory of standing on inch-wide footholds high up in the middle of the slab thinking "you have to get these next moves exactly right or else". Deep breath. Switch into careful and precise mode and work it out move by move. The huge jugs as you reach the arete are whoop-inducing. The ridge above seemed a romp afterwards (it isn't sharp so arete is a bit of a misnomer), but when you come up the easy way from the right it seems quite tricky in places, which is why it's sometimes graded Moderate. Every time I'm there it always seems harder than I remember it. It's reputedly a superb winter Grade III but although I've done it with snow on the ledges I didn't feel that I could count it as a proper winter climb.

Clogwyn y Person, Snowdon

Clogwyn y Person, with the scary slab of the Direct Start prominent

In winter the shelf which slants along the foot of the cliff above the lower broken rocks is a fun route, The Ramp, Grade II. It sometimes develops an ice pitch at the bottom but is mainly snow. Because it's right at the bottom of a north-facing cliff it doesn't get much sun and good nêvé can persist on it when other routes in the cwm are either stripped or slush.

The Ramp, Cwm Glas Mawr, Snowdon

Looking down the Ramp, the snow was much crisper than it looks!

The best known winter route in the cwm though is Parsleyfern Gully. This is right at the back of upper Cwm Glas and although it marks the edge of the steeper ground it does feel like a proper gully. It collects snow readily and comes into condition fairly often by Welsh standards. The first time I did it was in thick mist, and a group of about a dozen oldish guys were milling around in the floor of the cwm, looking slightly lost. It's still the only time I've met more than three people in the cwm. One of them asked where I was heading and then they all started to follow me. I didn't fancy climbing in a horde so put some speed on. At the foot of the gully was mountain guide Malcolm Campbell with a couple of clients and his jaw dropped as an endless train of people kept appearing out of the mist. He later wrote a very funny article for Climber about the National Park Authority opening a new path up Parsleyfern Gully. By the time we had all climbed it there probably was a major trail.

Parsleyfern Gully, Crib y Ddysgl, Snowdon

Parsleyfern Gully

One of the things I like most about Cwm Glas Mawr is the secretiveness of its two lakes. Both Llyn Glas and Llyn Bach are tiny, and both are perched on shelves underneath Clogwyn y Person so you don't see them until you're pretty much on their shores. Llyn Glas has a lonely little island, on which Black-Headed Gulls nest, with a very photogenically-positioned tree. There's some wonderful crumpled country on its outside edge, with rock slabs and boulder fields galore. One of the mounds has recently turned up in a peak-baggers list and although I've scrambled around there plenty of times I've no idea whether I went to the highest bump or not. Another excuse to go back there 😁.

Llyn Glas, Snowdon

Llyn Glas

Llyn Bach is higher and tucked in right against the cliffs, so it's the columnar mass behind that gives the appeal. It always seems to be absolutely freezing, and can disappear in winter. The stream that issues from it tumbles down below Cyrn Las in a series of waterfalls, and the right bank of these makes a good scramble. It begins with a surprisingly tricky move across a steepish slab, which looks completely innocuous until you try it. It's avoidable further right.

Afon Las, Cwm Glas Mawr, Snowdon

Afon Las below Cyrn Las, the scramble goes up the RH side

Further down and left are several other little gorges that are also fun scrambles. These are both easier and usually carry less water so you tend to follow the stream bed, although the slabbier parts of the intervening crags are fun too. Left of the lowest stream the ground starts to steepen into the West Wing of Dinas Mot and become climbing ground (though few climb there these days). The outside edge of this claims to be a V Diff called Bon Mot. The initial slab is indeed V Diff but after that it feels more like a scramble, with awkward moves here and there but separated by comfortable ledges. I did it once in early April and it made a great prelude to a round of the Snowdon Horseshoe in excellent winter conditions.

Cwm Glas Mawr, Snowdon

Intermediate Slabs, between the lower gorges

That's the attraction of the cwm really, there's an endless set of variations, which can be either used as a start to a round of the tops or be ends in themselves. I've had twenty-odd trips into it and can still think of half a dozen things I'd like to do there. In exploring those I've no doubt that I'll find half a dozen more. It's an inexhaustible place.

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