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Elidir Fawr – The Best Walks Up

By Dave Roberts   

Published – February 10, 2023

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Elidir Fawr – The Best Walks Up


Elidir Fawr is probably best known as the quarry scarred mountain next to Llanberis. While some parts of the Dinorwig quarries are interesting, this side of the mountain is irreparably scarred. However, don’t let first impressions put you off walking Elidir Fawr as it has some truly spectacular views and facets you wouldn’t believe from Llanberis. It’s been given the nickname ‘Electric Mountain’ as it’s a pump storage power station – or what is essentially a huge battery. The lake at Marchlyn Mawr acts as a storage reservoir, with the water only pumped down to generate electricity at peak times. So when all those kettles go on at the commercial break (do people really still watch TV with ads in this day and age?) it can jump into action and sell electricity to the grid at inflates prices. They can do this as they then pump the water back up to the top at times of low demand, and so the electricity to do so costs practically nothing. This is the one and only mountain that runs on Economy 7.

Elidir Fawr can be tackled from any of 4 locations – Llanberis, Nant Peris, Dinorwig and from Ogwen / Bethesda. As always with these articles, there’s always an element of overlap as routes converge towards the summits and you can technically start the walk anywhere you want if you’re willing to walk to the starting points above.

So How Hard is the walk up Elidir Fawr?

Most paths are poor to good for route finding, as in they are largely obvious but do occasionally have spots where you can lose the path and get lost. The easiest path is the one from Y Garn, which is wide and straightforward to follow. The route up via the quarries does not have access – so for information only. The route from Bethesda is the trickiest as it is pathless in places and seldom walked, one for those with excellent navigational skills only!

The routes vary from only around 3km (Nant Peris and via Elidir Fach) to around 6km – Via Carnedd y Filiast and from Llanberis, or can be walked as part of a much longer traverse to include Y Garn and Glyderau.

You’ll also need to check out the Weather Forecast: Met Office Snowdonia Mountain Weather

Getting Here, Parking and Public Transport.

Llanberis, Nant Peris and Deiniolen have frequent buses from Caernarfon and Bangor. With care you may be able to plan a loop around the buses. Some walking will be required to reach the start of the Marchlyn route from Deiniolen. Bethesda has a bus route from Bangor. The Bethesda route starts a few kilometres outside Bethesda but can be reached by following the Lon Las Ogwen.

Parking is not too problematic unless it’s a bank holiday. Plenty of paid parking can be found around Llanberis, there’s a sizeable Park and Ride car park in Nant Peris and limited roadside parking at Marchlyn and near Bethesda. Plentiful roadside parking is also available at the Dinorwig alternative start to the quarry route.

Pubs, Cafes and other Facilities

Plenty of facilities for walkers can be found in Llanberis and Bethesda including shops, cafes and a good selection of pubs. There’s a pub in Nant Peris (Faenol Arms) as well as toilet at the Park and Ride. There’s a small shop, cafe and pub (Wellington) in Deiniolen. Note that the Lodge Dinorwig no longer has a café and in these post pandemic times it’s wise for you to check what facilities are still open before you set out.

Why is it called Elidir Fawr?
According to – Enwau Eryri (Iwan Arfon Jones) Elidir Fawr was original name is Carnedd Elidir, Elidir’s Cairn and  renamed Elidir Fawr, along with Elidir Fach in order to correspond to the naming of Glyder Fach and Fawr. The identity of this legendary Elidir is lost to time. 

Whichever route you choose to take, you’ll need some mountain experience and you’ll know how to use a map and compass. You’ll find a rundown of these routes below with the full route guide free of charge on our partner site – Mud and Routes. Remember that only a summary of the walk is provided below – you’ll need to click through to read the full walk guide.

Note that times quoted are for the ascent route only! Owing to the nature of hillwalking, allow about the same time for descent, maybe a little less depending on the nature of the route. Times quoted are particularly conservative, and include time to enjoy the route, but obviously the actual time to be taken will depend both on the individual and the conditions prevalent on that day.

Map Showing Best Walks Up Elidir Fawr

Click on the individual lines on the map below to see the labels. Each colour is also noted in the article.

You will need to buy the proper OS map and we recommend either the  OS Explorer OL17 Snowdon & Conwy Valley or the wonderful Snowdonia BMC (British Mountain Map) from Harvey Map

Best Day out on Elidir Fawr – Marchlyn Horseshoe or Loop

The route from Marchlyn / Deiniolen and Elidir Fach and descending via Carnedd y Filiast is the one best outing in our opinion. Extending this route to include Y Garn as well, makes this one of the best routes in the Glyderau outside the usual Ogwen suspects. We also love the full traverse of the Glyderau, starting from Deiniolen / Marchlyn, but unfortunately Elidir Fawr isn’t the highlight of that walk.

Straight up Elidir Fawr from Nant Peris (green) the relentless direct slog.

Ok, maybe when we said there were impressive sides to Elidir, we probably shouldn’t open with the Nant Peris slog. It is only around 3km long, with 600m of ascent, and should take around 2-3 hours to complete. While the lower reaches of Cwm Dudodyn is pleasant enough, the slog from here to the summit has no redeeming features other than ending at the summit.  Once you do arrive at the summit, you’ll forget that slog ever happened and you can now enjoy the view .

Note that the walk takes the most direct line from the footbridge shown at SH608 595 rather than following the right of way shown on the map up the valley as I did on my first mountain outing. Elidir Fawr was my first ever mountain. I was 14, the mountain was a bit older and much more experienced than I was. Of course, I was easily led astray and ended up on steep scree high above Dudodyn. How I got to the summit was anyone’s guess, I returned under a month after to try again, and managed a better line if not the official one. I listened to the Mandela 70th birthday Concert on the summit (headphones), so you can pinpoint the date if you wish.

Via Dinorwig Quarries from Llanberis (blue)/ Dinorwig (light blue)

The walk up Elidir Fawr from Llanberis works out at just shy of 6km with 870m of ascent – making it the longest route in total, but only just, and should take a good 3 hours. This route eventually joins the Elidir Fach from Marchlyn route, though the final section onto Elidir Fach is far from elegant and quite pathless. This is one for lovers of quarries, though you can’t actually walk this path as access is blocked so we include this for information only. The walk from Llanberis following the zig zags and then via the Anglesey Barracks is one of the highlights of this route.

Alternatively, you can set up from the Interchange at Dinorwig (light blue) and shave off some of the initial climb from Llanberis. It’s also much quieter than Llanberis, and parking can be less of an issue and it’s also easy enough to get to by bus.


From Marchlyn / Deiniolen via Elidir Fach (orange)

Now we’re getting to the good stuff. While the initial reservoir road is anything but inspiring, you’re soon on open hillside climbing above Marchlyn Bach. After a reasonably short grassy slog, the plateau of Elidir Fach makes pleasant enough walking and absolutely stunning views. A short pull up a scree path brings you out on the summit ridge, and a short clamber to the summit shelter. You can walk the Marchlyn Horseshoe or Loop by combining with the next route.

Alternatively, this makes a good start to a full traverse across the Glyderau from Deiniolen over to Capel Curig.

Being 3.5km long and only 550m of ascent – makes this by far the least strenuous route, but with significant off path sections and some navigational skills, that doesn’t make it easy.

Via Carnedd y Filiast (red / purple)

This is the longest route at just over 6km and 675 metres of ascent from Marchlyn (red), and should take around 3 hours. The route from Bethesda (purple) is shorter at 4.5km but packs in 820m of ascent and a lot of tricky ground, so again allow at least 3 hours. This starts at same location as the previous walk, but stays on the reservoir road for much longer. It does mean that by the time you’ve reached the hillside that a good chunk of the climbing has already been done. The route continues up Carnedd y Filiast to Mynydd Perfedd,  with impressive views across Marchlyn Mawr towards Elidir. The airy ridge walk high above the reservoir between Mynydd Perfedd and Elidir a particular highlight if you can keep to the crest, but be warned that  you’ll easily miss this section if you keep to the path. It isn’t quite Crib Goch, but it’s a decent enough diversion while it lasts. I prefer the route in reverse as part of the Marchlyn Loop, using this as a descent

Alternatively you can start from around 2km south of Bethesda you can ascend Carnedd y Filiast by way of a faint path. The going isn’t easy to start with, but the path becomes more obvious as you climb. Can be made into a circuit by descending via Y Garn to Ogwen and following the old road back to the start.

Elidir Fawr from Y Garn  (yellow)

Adding Elidir Fawr to an outing of Y Garn will add a whopping 4km, 320m of ascent and around 1.5 hour for a one way trip, which would add 8km if you needed to return to the summit of Y Garn. That excludes the summits of Mynydd Perfedd and Y Foel Goch, which will add another 100m of ascent and 0.5km to the walk.

Of course, how you get to Y Garn is another article altogether! You can also include Y Garn as a dog-leg to the Marchlyn Horseshoe / Loop which turns that walk into a fuller more satisfying day without feeling you’ve gone too far out of your way. You can include or exclude Y Foel Goch as you see fit.

You can also set off from Nant Peris and include both Elidir and Garn as a natural circuit or include Elidir Fawr as a dog-leg to any route up Y Garn.


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Dave Roberts

Dave Roberts founded Walk Eryri in 2004, with the aim of providing routes that are off the beaten track. Walk Eryri is now part of Mud and Routes which continues to provide more off beat routes and walks in Snowdonia and beyond. Dave has been exploring the hills of Eryri for over thirty years, and is a qualified Mountain Leader. Dave also established Walk up Snowdon, Walk up Scafell Pike and Walk up Ben Nevis just to mention a few.

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