Llyn Idwal

Llyn Idwal is Wales's most important mountain lake — the centrepiece of the country's first National Nature Reserve, a site of outstanding geological significance, and the location where Charles Darwin gathered evidence that helped shape his understanding of glacial action in 1842. The surrounding crags hold some of Wales's finest rock climbing; the lake shore supports plants that have grown here since the last ice age.

The Lake

Llyn Idwal sits in Cwm Idwal, a classic glacial cwm surrounded on three sides by dramatic cliffs. The Idwal Slabs — great sheets of smooth rhyolite rising above the lake — have been a training ground for British rock climbers since the 1890s and remain one of the most popular beginner climbing venues in Wales. Behind and above them, the dark slot of Twll Du (Devil's Kitchen) cuts into the cliff face, a deep cleft through which waterfalls cascade in wet weather.

The lake was declared a National Nature Reserve in 1954 primarily to protect the arctic-alpine plant communities that have persisted on the ledges and crags since the retreat of the ice. Tufted saxifrage, alpine meadow-rue, mountain avens, and other species that are otherwise found only in the Scottish Highlands or the high Alps grow here in accessible profusion.

Getting There

A good path leaves from Ogwen Cottage on the A5 (SH 649 603) and reaches the lake shore in about 20 minutes. The full circular walk around the lake — 5 kilometres — takes 1.5 to 2 hours and is one of the finest short mountain walks in Wales, combining the lake shore, the base of the Idwal Slabs, and a view into Twll Du. The path is well maintained by Natural Resources Wales and is suitable for most walkers in reasonable footwear.

What You Will See

The Idwal Slabs are almost always busy with climbers in good weather — watching parties ascending the classic slab routes is a pleasure in itself. Peregrine falcons and choughs nest on the surrounding cliffs. In spring the arctic-alpine plants come into flower on the ledges above the lake; information boards along the path identify key species. The geology is exceptional — glacial striations on the lakeside rocks, classic roches moutonnees, and the dramatic folded cliff structures above Twll Du tell the story of repeated glaciation in vivid detail.