Cwm Glas Routes

Page Type Page Type: Route
Location Lat/Lon: 53.07206°N / 4.08005°W
Additional Information Route Type: Hiking
Seasons Season: Spring, Summer, Fall, Winter
Additional Information Time Required: Half a day
Additional Information Difficulty: Just walking
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The Cwm Glas routes are the quietest of Snowdon's walking routes and are subsequently the most pleasant. There are two starting points, one at Pen y Pass the other at Ynys Ettws, the latter of which is the shortest. The routes are special because they take the walker around the lesser-seen parts of Snowdon; the views of Crib Goch and Clogwyn y Person from the Cwm Glas Mawr are truly spectacular. The fact that this part of the mountain is so quiet means that it offers a truly unique experience.

Getting There

The starting point for the first Cwm Glas Route is the Pen y Pass car park (SH 647 555) at the zenith of LLanberis Pass, which can be reached easily by road on the A4086 that runs between Llanberis (SH 582 598) and Capel Curig (SH 719 580).

Owing to the popularity and number of the routes that start here,the Pen y Pass car park often fills up quickly so if you want to park there a very early start is recommended. Luckily there are other options, the first of these is an excellent park and ride which runs regularly all day (including weekends and bank holidays) from Nant Perris (SH 607 582). The second option is the

Snowdon Sherpa bus service which has various stops around the mountain and runs from Llanberis, Bettws y Coed, Caernarfon, Beddgelert, Bethesda and Porthmadog. Be sure to check timetables first as you don't want to end up missing the last bus and find yourself stuck, of course in these situations hitching is always an option.

The second route starts at Ynys Ettws (SH 622 568) which is around halfway up the Pass of Llanberis. There is some parking on the roadside and the Snowdon Sherpa also stops there.

Route Description

The first route (red, see map, approx. 6km) starts at Pen y Pass (SH 647 555) and follows the same path as the Snowdon Horseshoe and PYG Track, but deviates from them at Bwlch y Moch (SH 628 552) where it takes a rather indistinct path, marked by a small cairn and contours around the eastern margins of Crib Goch. The route hugs the base of North Ridge and passes through a shallow col (SH 624 559) between the knoll that caps Dinas Mot (SH 624 562). Its best not to drop any height and aim for a notch in the North Ridge well above Dinas Mot. If you drop down into Dinas Mot there is a very steep and awkward climb back up which crosses a waterfall and can be dangerous when if full flow.

From the North Ridge the path is partially lined with cairns and follows the shape of Cwm Uchaf around the base of Crib Goch's pinnacles and Crib y Ddysgl towards the base of the Clogwyn y Person Arête (SH 616 556). The path follows the base of the Arête around to its western side where it reaches the pond of Llyn Bach (SH 615 555). From here the route ascends the east facing part of the Llanberis Ridge (which the Snowdon Mountain Railway runs up) and takes the grassy slope between a scree gully on the left and steep cliffs on the right. After a short and easy scramble at the beginning of the slope the route turns back into a path taking the walker onto the ridge just above the Clogwyn Station (SH 607 561). From here the path joins the Llanberis Path and travels south to Snowdon's summit.

Crib Goch from Clogwyn y PersonCrib Goch and Cwm Glas from Clogwyn y Person

The second route (violet, see map, approx 5km) is more physically strenuous forcing the walker to ascend over 2,000 feet over a very short distance. The extra effort is definitely worthwhile as the atmosphere of being enclosed in the cwm, with Crib Goch ridge demonstrably on the skyline. The route starts at a small bridge over the Afon Nant Peris near Blaen-y-Nant (SH 622 568). After crossing the bridge and going over a stile, the path crosses another small bridge (made of railway sleepers), and sharply turns to the left and follows a rather indistinct path up the right bank of the stream. It then heads through a gap between Craig y Rhaeadr on the left and the rockface of Gyrn Las on the right, the route from here is wither directly but steeply up the left side of the stream, or by the slightly easier route through a shallow gully further to the left. Both routes are steep and travel over loose rock. By crossing two other streams and scrambling up a short bank the path reaches Llyn Bach where it joins the first path and ascends the Llanberis Ridge.

Essential Gear

Just a good pair of boots, waterproofs and some lunch. If walking in winter make sure you also carry an ice axe and crampons.


Open Space Web-Map builder Code
Navigation Maps

OS 1:25k Explorer Series OL 17 Snowdon/Yr Wyddfa

OS 1:50k Landranger Series 115 Snowdon/Yr Wyddfa

Harvey Map Services 1:25k: Snowdonia North: Snowdon, Glyders, Carnedds

Harvey Map Services 1:25k: Snowdon

Harvey Map Services/BMC 1: 40k British Mountain Map: Snowdonia North

Road Maps

OS Travel Map 10 Wales/Cymru & West Midlands


External Links

Llyn GlasLlyn Glas, Snowdon

Government Bodies and Official Organisations

Snowdonia National Park Authority

Council for National Parks

Association of National Park Authorities

Natural Resources Wales


Royal Commission on Ancient & Historical Monuments in Wales

Gwynedd Archaeological Trust

Snowdonia Society

The National Trust

Hiking, Climbing and Mountaineering Organisations and Companies

British Mountaineering Council

The Climbers’ Club


Plas y Brenin National Mountain Centre

Hightreck Snowdonia


Mountain Weather Wales

Weather from the Met Office

BBC Weather

Tourist Information

Visit Wales

North Wales Tourism Partnership

Local Information from

Local Information from Snowdonia Wales Net

North Wales Index


Welsh Public Transport Information

UK Train Timetable


Youth Hostel Association in Wales

Pete's Eats

Pen-y-Gwryd Hotel

Maps and Guidebooks

Ordnance Survey

Harvey Map Services

Cicerone Guidebooks

Climbers’ Club Guidebooks


North Wales Bouldering

Cordee Travel and Adventure Sports Bookshop

Wildlife and Conservation

Joint Nature Conservation Committee

Natur Gwynedd

North Wales Wildlife Trust

Royal Society for the Protection of Birds



Parents refers to a larger category under which an object falls. For example, theAconcagua mountain page has the 'Aconcagua Group' and the 'Seven Summits' asparents and is a parent itself to many routes, photos, and Trip Reports.