On a British Mountaineering Council (BMC) panel about running the Welsh 3000s, Sarah Ridgway of Run Snowdonia gave a warning. “Elidir Fawr will break you,” she said.
She meant its “relentless grassy slope”. The climb starts at Nant Peris, near Llanberis, and rises steeply to the boulders of the 924 m summit.
Starting at Nant Peris
The route from Get Lost Mountaineering, a walking route website, starts at the large Nant Peris car park on the A4086.
The car park is about 4 km south-west of Llanberis. Coming from Llanberis, it is on the right, almost past the village.
The Eryri National Park Authority, which runs that car park, lists it on its parking page as parking for the Miners’ and Pyg Tracks. It also lists a park and ride from Nant Peris to Pen-y-Pass.
The Authority’s parking page, read in October 2026, says payment is by chip and pin or contactless only. EV charging is available on site.
Bring a card, because cash is not accepted.
Buses also stop here. The Sherpa’r Wyddfa bus network has a timetable with times from 28 March 2026.
We compile and explain public route and safety information. We guide nobody and sell nothing on the hill.
The steep climb up Cwm Dudodyn
The climb from Nant Peris is a “beast of an ascent”, according to Mud and Routes, a route website. It describes “a sadistic 800m of largely slogging on a steep slope”, with the only respite being the summit.
Get Lost’s route up from the car park goes like this:
- Walk towards Llanberis along the main road, past the Vaynol Arms pub.
- Take the first road on the right, just before a chapel.
- Go up the left side of a campsite to a white cottage, then follow the stiles to the path beside the Afon Dudodyn.
- Follow the path or track beside the Afon Dudodyn to a footbridge with a handrail, then cross the stream.
- Climb north across the side of the mountain.
- Higher up, the path zig-zags through a boulder field.
A later Get Lost route, walked on 7 May 2016, notes a hydro track going up Cwm Dudodyn for some distance. The path crosses it, and the crossing is signed.
Mud and Routes takes the obvious footpath into Cwm Dudodyn via Fron farm. It crosses the footbridge and makes for the summit.
Mud and Routes calls the mapped path to the ridge at the head of the valley “horribly eroded” and best avoided.
The boulder summit
The BMC lists Elidir Fawr at 924 m (3,031 ft), which makes it one of the Welsh 3000s. Get Lost Mountaineering also gives 924 m, with the grid reference SH 612 613.
On Get Lost’s route the path peters out about 50 m south of the summit. A short rough section then leads to the large shelter cairn.
A UKHillwalking route card by Nicholas Livesey, dated 2 September 2016, grants that it “may well be” hideously scarred and cruelly exploited.
The same card says Elidir Fawr is “often the choice of the connoisseur when a quick 3000er is the order of the day”.
Marchlyn Mawr and the power station inside the mountain
Dinorwig power station was built inside Elidir Fawr, says ENGIE, the company whose pages describe it. Water stored in the upper reservoir, Marchlyn Mawr, flows through high-pressure tunnels to the turbines.
The water collects in the lower reservoir, Llyn Peris. At off-peak times the six units are reversed as pumps and send it back up to Marchlyn Mawr.
ENGIE counts 16 km of underground tunnels deep below the mountain.
Dinorwig and Ffestiniog belong to First Hydro Company. Dinorwig was first commissioned in 1984 and can generate 1.8 GW within 12 seconds, according to ENGIE.
On the ridge, Get Lost’s route crosses Bwlch y Marchlyn, a narrow rocky arete overlooking the Marchlyn Mawr reservoir to the north. An easier path runs below on the right.
Get Lost calls the arete “reasonably straightforward in dry and calm conditions”.
The BMC’s access database says the Upper Dinorwig quarries are mainly owned by First Hydro. Access away from the designated footpaths is not permitted by the landowners, so stay on the public paths around the Dinorwig quarries.
The ridge on to Y Garn
Beyond the summit the ridge runs east towards Y Garn. On the way, go4awalk, a walking route website, names four places in its route summaries.
They are Bwlch y Marchlyn, Bwlch y Brecan, Foel-goch and Bwlch y Cywion.
Mud and Routes calls the path from the summit “rocky and narrow, but easy to follow”. It gives 3 km of high-level walking with no climbing before Y Garn.
Mud and Routes warns against two wrong turns: “the path that contours right” and “the second path that takes you up Foel-goch”.
The path up Y Garn is steep and zig-zags, says Mud and Routes. Its own route from Nant Peris over Elidir Fawr and Y Garn, coming down Llwybr y Carw, is 13 km.
It lists 1100 m of ascent, 4 hours and a grade of Hard.
The route up Y Garn from Ogwen reaches the same summit from the other direction.
Choosing the way down
Two ways off the ridge are documented, and both end back at Nant Peris.
- Back by Bwlch y Brecan and Esgair y Ceunant: Get Lost’s route for Elidir Fawr alone returns by the grassy Bwlch y Brecan. It passes below Foel Goch and Bwlch y Cywion. It then turns south-west down the Esgair y Ceunant ridge above Cwm Dudodyn. Get Lost gives that route, out by the Afon Dudodyn, as 10 km and approximately 6 hours. A later Get Lost route comes down the same ridge, then drifts right to the hydro track and the minor road back to the village.
- Over Y Garn and down Llwybr y Carw: Mud and Routes comes down towards Llyn y Cwn, then turns right along Llwybr y Carw. It calls the path “often steep and loose, usually with more than one option”. It also warns: “be careful at one point as the path stops in a sheer drop!”
Starting from Ogwen instead is another option. Get Lost says Elidir Fawr is “difficult to incorporate into a circular walk which takes in all the other Glyderau”, and that it is possible if one starts at Ogwen Cottage.
None of the Sherpa’r Wyddfa routes on its timetable page ends at Ogwen, so plan your way back before you set off.
Where Llwybr y Carw stops in a sheer drop, take the footpath to the left.
