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View of the Idwal Slabs in Cwm Idwal Valley, Carneddau and Glyderau, Gwynedd, Wales
Cwm Idwal Valley in Snowdonia, Wales | © National Trust Images/Chris Lacey

Cwm Idwal walk

This moderately strenuous walk offers some of the most dramatic mountainous scenery in the UK at the oldest National Nature Reserve in Wales. Explore beautiful ice-sculpted Cwm Idwal – a bowl-shaped hollow filled with the crystal clear waters of Llyn Idwal, world famous for its rock formations and rare and fragile plant life.

Avoid parking worries by hopping on the bus

At busy periods, the limited parking fills quickly. There are a couple of more sustainable options available with a park and ride from nearby Bethesda. The T10 buses run frequently between Bangor and Corwen as well as Bws Ogwen, a local electric shuttle bus, which runs regularly between Bethesda and Capel Curig. For further details, please see 'Getting there' section.

Total steps: 11

Total steps: 11

Start point

Ogwen Cottage and Ranger Base, grid ref: SH 650603

Step 1

From the Ogwen Cottage Ranger Base, walk in a westerly direction for roughly 93 yd (85m) over the bridge to the Cwm Idwal Visitor Centre building. Steps to the left of the building are the start of the path which ascends steeply at times for approximately 56 yd (50m) through verges of heather, towards the mountain gate.

Step 2

Continue through the gate and over the oak bridge. The oak bridge was replaced in the summer of 2010 using sessile oak sustainably harvested from the nearby National Trust place at Plas Newydd. The bridge provides an excellent opportunity to photograph the peak of Y Garn, with Afon Idwal in the foreground.

Step 3

The footpath meanders in a south-eastern direction for 550yd (500m) before arriving at a junction. Take the right fork towards the west along the more formal stone-surfaced path, and follow for another 550yd (500m) to the lake.

Step 4

At Llyn Idwal (lake) you may choose a clockwise or anti-clockwise route around the nature reserve. This guide takes you on the clockwise option. Before setting off along the eastern lake shore, look left, a few yards above the footpath. Here you'll see a collection of large fractured rocks known as Darwin Idwal Boulders.

Visitors relaxing on rocks known as Darwin Idwal Boulders in Cwm Idwal Valley with Pen yr Ole Wen in the background in Carneddau and Glyderau, Gwynedd, Wales.
Visitors relaxing on the Darwin Idwal Boulders in Cwm Idwal Valley, Gwynedd | © National Trust Images/Chris Lacey

Step 5

The footpath follows the lake shore towards the south for 550yd (500m), until you arrive at a gate through a wall. The wall is there to exclude grazing animals from the nature reserve and to allow the regeneration of natural upland vegetation. Opposite the wall is a small island of rock in the lake. The vegetation growing there gives us a glimpse of how the Cwm may appear in years to come, without the grazing pressure of sheep and cattle.

Step 6

Once through the gate the path begins to rise gently as you climb over mounds of rock debris (moraines) left behind as glaciers retreated from the cwm around 10,000 years ago.

Step 7

You are now approaching the famous Idwal Slabs, a training ground for many pioneering mountaineers including Everest conqueror Edmund Hillary and his Welsh team mate Charles Evans. Roughly 55yd (50m) before the base of Idwal Slabs, follow the path down right towards a level area, using the stepping stones to cross streams. NB: An alternative high level route may be taken at this junction by following the path towards Idwal Slabs and up towards the base of the cliffs above. This route should only be attempted by competent hill-walkers as it involves very rough, steep ground.

Step 8

Look up to your left and you'll see the sheer cliffs which form the headwall of Cwm Idwal, known as Twll Du in Welsh or 'The Devil's Kitchen'.

Step 9

The path rises gradually until you reach the junction of the high level route as it descends through the boulder field. Take a right turn onto this path and walk into an area of heather-clad hummocks.

Step 10

The path climbs gradually through the moraines before descending gently towards the lake shore. Once across the footbridge over Afon Clyd, which tumbles steeply from a hanging valley to your left, go though the gate in the wall. You're now on a shingle beach on the north-west shore of Llyn Idwal. Take a moment to look to the back of the Cwm and absorb the scale of this natural amphitheatre. Try to imagine the area lying beneath a blanket of ice hundreds of metres thick, a mere hundred centuries ago.

Step 11

Follow the lake shore around to the east, until you arrive at a gate through a wall, leading to a slate bridge that crosses Afon Idwal as it drains out of the lake. Once across, you’ll have completed the circular walk around the lake and can retrace your steps to the Ogwen Cottage Ranger Base.

End point

Ogwen Cottage and Ranger Base, grid ref: SH 650603

Trail map

Ordnance survey map of Cwm Idwal walk in Carneddau and Glyderau, Wales
Trail map for Cwm Idwal walk | © Crown copyright and database rights 2012 Ordnance Survey

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Get in touch

National Trust, Bwthyn Ogwen, Nant Ffrancon, Bethesda, Gwynedd, LL57 3LZ

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