Glaciation has left hundreds of lakes across Eryri, each with its own character. From the copper-green tarn beneath the summit of Yr Wyddfa (Snowdon) to the long ribbon of Llyn Tegid, these are detailed guides to the most significant.
In Welsh a lake is a llyn (plural llynnau), and you will see the word on every map. Broadly, the lakes of Eryri (Snowdonia) fall into two groups. The high cwm lakes, such as Glaslyn and Llyn Idwal, sit in bowls scooped out by Ice Age glaciers and are reached on foot. The valley lakes, such as Llyn Padarn, Llyn Gwynant, Llynnau Mymbyr and Llyn Tegid, lie beside main roads and villages, which makes them the easiest to enjoy on a short visit, in poor weather or with young children. Our geology guide explains how the ice shaped them.
The Lakes at a Glance
| Lake | Area | Access | Best for |
|---|---|---|---|
| Glaslyn | Yr Wyddfa, east side | On foot from Pen-y-Pass via the Miners’ Track or Pyg Track | Mountain scenery, mining history |
| Llyn Idwal | Ogwen Valley | Short, steep walk from the Idwal Cottage visitor centre on the A5 | A short mountain walk, geology, plants |
| Llyn Tegid | Bala, southern Eryri | Roadside, with the town at its northern end | Watersports, lakeside railway, families |
| Llynnau Mymbyr | Capel Curig | Beside the A4086 west of the village | The classic Snowdon Horseshoe view |
| Llyn Padarn | Llanberis | Roadside and lakeside paths from the village | Easy walks, kayaking, the lake railway |
| Llyn Gwynant | Nantgwynant | Beside the A498 between Beddgelert and Pen-y-Gwryd | Valley views, swimming, camping |
The Lakes
Glaslyn
The high mountain lake directly beneath the summit of Yr Wyddfa, with its extraordinary copper-green colour from dissolved minerals and the ruins of the Britannia Copper Mine on its shore.
Llyn Idwal
The heart of Wales’ first National Nature Reserve. Darwin visited in 1842. The Idwal Slabs above, arctic-alpine plants on the cliffs and the dark slot of the Devil’s Kitchen. One of the great short walks in Eryri.
Llyn Tegid
The largest natural lake in Wales: 6km long, 42m deep and home to the gwyniad, a fish found nowhere else on earth. The Bala Lake Railway runs along its southern shore.
Llynnau Mymbyr
The twin lakes at Capel Curig produce one of the most famous views in Eryri: the Snowdon Horseshoe reflected in still water. A calendar photograph waiting to happen.
Llyn Padarn
The lake beside Llanberis, shaped by the slate industry. Dolbadarn Castle on its rock sill, the Llanberis Lake Railway along its shore and arctic char in its depths; read the story of the torgoch of Llyn Padarn and the fight to save them.
Llyn Gwynant
One of the most beautiful valley lakes in Eryri, stretching through Nantgwynant beneath wooded slopes. Wild swimming, the nearby start of the Watkin Path and one of the finest valley drives in Wales.
Around Cwm Idwal and Ogwen
- Cwm Idwal: the glacial corrie that holds Llyn Idwal, with its Darwin connection and rare arctic-alpine plants.
- Ogwen Valley: gateway to Tryfan, the Glyderau and the Carneddau, with Llyn Ogwen at its head.
Choosing a Lake
If you have one free morning and decent weather, the circuit of Llyn Idwal is hard to beat: the National Trust puts it at around 3 miles on rough, sometimes steep paths, and it packs moraines, cliffs and rare plants into a walk most active families can manage. For Glaslyn, the Miners’ Track from Pen-y-Pass climbs gently past Llyn Teyrn and Llyn Llydaw before a steeper final pull, so you see three lakes in one outing without going near the summit. If the cloud is down, stay low: Llyn Padarn, Llyn Gwynant and Llyn Tegid all have lakeside paths and are still atmospheric in rain. Several feature in our easy family walks in Eryri.
Photographers should look at the photography guide; the still-water reflections at Llynnau Mymbyr and Llyn Gwynant are usually best early in the morning before the wind gets up.
Practical Tips
- Parking: Pen-y-Pass, the start for Glaslyn, has run a pre-booked parking system in the busy season, and the Ogwen car parks fill early on fine weekends. The Sherpa’r Wyddfa buses link Pen-y-Pass with Llanberis, Nant Peris, Caernarfon and Bangor, and buses also serve the Ogwen Valley. See our parking and transport guide.
- Swimming: the water is cold all year, and cold-water shock is a risk even on hot days. Swimming and water sports are not allowed at Llyn Idwal, which lies within a nature reserve, and some lakes are drinking-water reservoirs or on private land. Llyn Tegid, Llyn Padarn and Llyn Gwynant are among the places the National Park Authority lists as popular for swimming. Read our wild swimming guide first, and our article on where to swim and how to stay safe.
- Algae: blue-green algae has been recorded on Llyn Tegid in some summers. Check the National Park Authority’s latest notices and keep dogs out of the water if a warning is in place.
- Emergencies: call 999 and ask for Police, then Mountain Rescue.
Frequently Asked Questions
What is the largest lake in Eryri?
Llyn Tegid at Bala is the largest natural lake in Wales, around 6km long. Some reservoirs, such as Llyn Trawsfynydd, are large too, but they are man-made.
Which lake is easiest to visit without a long walk?
Llyn Padarn, Llyn Gwynant, Llynnau Mymbyr and Llyn Tegid all sit beside roads. Llyn Idwal needs a short but steep walk from the A5.
Can I swim in Llyn Idwal?
No. Llyn Idwal lies within the Cwm Idwal National Nature Reserve, where swimming and water sports are not permitted, to protect the lake and its plants.
Why is Glaslyn so green?
Its colour comes from dissolved copper and other minerals from the rocks around it, which were mined on its shores for well over a century.
