The lake that steadies the Severn
Llyn Clywedog is a 615-acre reservoir in the hills off the B4518 near Llanidloes, created when the Clywedog Dam was built between 1963 and 1967. The dam is a national record-holder: at 72 m (236 ft) it is the tallest concrete dam in the United Kingdom, and its job is to regulate the flow of the River Severn — holding back the winter floods and topping up the river in dry summers. The result, whatever the engineering intent, is one of Mid Wales’s most beautiful sheets of water, winding for miles between steep sheep-grazed hillsides, with viewpoints above the dam looking down the whole silvered length of it.
Fishing, sailing and red kites
Clywedog has quietly become an outdoor hub. The lake is renowned for fly fishing, it has its own sailing club, and red kites are a regular sight tilting over the water — the moment a kite banks against six hundred acres of silver is worth the drive on its own. Even if you do nothing more energetic than park above the dam with a flask, the combination of big water, big hills and big birds makes it a rewarding stop; see our wildlife page for more on the kites and where else to find them, including the daily 2pm feeding at Bwlch Nant yr Arian. Bring binoculars if you have them — the scale of the place swallows detail, and the far shore is a long way off.
The valley under the water
All of this was farmland within living memory. Building the dam between 1963 and 1967 drowned some 615 acres of the Clywedog valley, farms and all, and the loss was fiercely resented: on 6 March 1966 the site's overhead cableway was bombed, causing around £30,000 of damage and setting the works back six months, in an attack widely attributed to Mudiad Amddiffyn Cymru. What came of it is a concrete buttress dam 72 m high and around 230 m long, holding roughly 50,000 megalitres, regulating the Severn and supplying about 50 million litres of drinking water a day to the West Midlands, with a 500 kW turbine making it self-powering. Nature has taken to it: an osprey platform installed here in 2005 has raised 22 chicks since 2014, with a webcam on the nest — see our ospreys page for the better-known Dyfi birds.
Bryntail: a lead mine at the foot of the dam
Directly below the dam wall, free to walk into, are the ruins of the Bryn-tail lead and barytes works, in Cadw's care and a scheduled monument, three miles north-west of Llanidloes off the B4518. This was a working industrial site until it closed in 1884, and an unusual amount survives: crushing houses, ore bins, roasting ovens, water tanks, a barytes mill, the smithy and the manager's office, around Gundry's shaft. Entry is free, open in daylight hours, with parking above and a ten-minute walk downhill through trees; the ground is uneven, with steps, slippery surfaces after rain and unstable masonry, so wear proper shoes. For more old workings, the slate country around Corris is the other great industrial landscape near Machynlleth.
The mountain road via Dylife
The best reason of all to come is the getting there. The 20-mile scenic mountain road between Machynlleth and Llanidloes climbs over the roof of Mid Wales via the remote upland hamlet of Dylife, and passes the Wynford Vaughan-Thomas memorial viewpoint near Foel Fadian — a toposcope marking the spot where the great broadcaster judged the view towards Snowdon the finest panorama in Wales. On a clear day the whole of northern Wales seems to stand along the horizon. Foel Fadian (510 m) is also the highest point of Glyndŵr’s Way, the 135-mile National Trail from Knighton to Welshpool that passes through Machynlleth on the way — from the summit ground nearby, the view runs down the Dulas valley to the town and out to the sea, so walkers and drivers share the same panorama.
The route runs roughly like this. From Llanidloes the B4518 mountain road heads north-west into the Cambrian Mountain uplands; near that end lie Hafren Forest and the trails to the source of the Severn on Pumlumon, with red kites overhead. It then passes Llyn Clywedog, where ospreys nest in summer, climbs to the old lead-mining settlement of Dylife and its gorge, and crosses the tops to the Wynford Vaughan-Thomas viewing point before dropping down the Dulas valley into Machynlleth.
Making a circuit
The classic day is a loop: out from Machynlleth over the mountain road, pausing at the viewpoint; on past Dylife and down to the lake and dam; then either back the same wild way or a longer return through Llanidloes. Allow a half-day for the straight out-and-back, and a full day for the loop with proper stops at the toposcope, the dam overlooks and the lake shore. It combines naturally with other inland trips — Devil’s Bridge lies on the far side of the same upland mass — and walkers can sample Glyndŵr’s Way from several points along the road (see our walking page). The route is single-track in places with mountain gradients: take it slowly and enjoy it. More ideas on our day trips page.
Practical Information
The lake lies off the B4518 near Llanidloes; the mountain road from Machynlleth via Dylife is about 20 miles of slow, spectacular driving — allow the best part of an hour each way and check conditions in winter, as this is genuinely high, exposed country, single-track in stretches with passing places. There is no public transport along the mountain road, so this is one day out that really does need a car — or determined legs, since Glyndŵr’s Way crosses the same hills. Viewpoints and the dam overlooks are free to enjoy; fishing and sailing are run by their respective clubs — check locally for day arrangements. Fill up with fuel and picnic supplies in Machynlleth or Llanidloes before you set out; there are no services on the tops. The Dylife mountain road is the scenic way to reach the reservoir from Machynlleth.
Day trips