From Llanrhystud to Llyn Brianne

Leaving Llanrhystud and heading towards Tregaron feels like the beginning of a gentle adventure — but don’t be fooled. If you think some of the roads you’ve already travelled are small, just wait until you leave the old market town of Tregaron. This is not a route for new drivers or anyone who breaks into a sweat at the thought of reversing uphill around a blind bend, with a tractor bearing down on them. (or in my case a logging lorry - seriously).

Make sure you pick up any last‑minute supplies in Tregaron. Llyn Brianne has no facilities whatsoever, so hopefully you’ve packed a picnic.

Into the Cambrian Mountains

The drive is, at times, nerve‑wracking, but it is also utterly stunning. The landscape becomes more wild and desolate the deeper you head into the Cambrian Mountains. You pass through classic U‑shaped valleys carved 20,000 years ago by the Welsh Ice Cap — the very reason Llyn Brianne sits where it does. The ice sheets had already sculpted a perfect flat‑bottomed trough, making it an ideal place for engineers to block and flood the Tywi river system.

Llyn Brianne is Europe’s tallest rock‑fill dam. It’s not as well known as the Elan Valley, which I actually like — fewer crowds, more solitude.

Facilities? None. Toilets? Yes — but no loo roll on this occasion. Cafés, gift shops, ice‑cream vans? Absolutely not. Bring a picnic and a sense of self‑sufficiency.

A Pause at Soar‑y‑Mynydd

Around 8–9 miles from Tregaron you’ll find a beautiful little chapel: Soar‑y‑Mynydd. You may welcome the chance to calm your heart rate here after the drive.

This is Wales’ most remote chapel — a small whitewashed building, usually open, with pews that smell wonderfully of old timber the moment you step inside. Built in 1822, it still holds services today. The Welsh inscription above the pulpit translates to “God is Love.” It is a good moment to enjoy the stillness and listen to the birds and the stillness.

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Towards the Dam

From the chapel, the road winds through Forestry picnic spots and viewpoints. The first is Fannog, where — when water levels are very low — the top of a ruined farmhouse emerges eerily from the reservoir.

Barriers are scarce, passing places plentiful, and sheep wander across the road with the confidence of animals who know they own the valley. They’re mostly unfazed by cars and traffic, and certainly not bothered by you/ewe.

Eventually the dam rises ahead, stark and impressive against the hills.

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Walking or Cycling at Llyn Brianne

There’s an 11 km looped walk starting at the dam, though I’ve yet to do it. I usually bring my road bike and explore the lanes instead — they’re like a rollercoaster for cycling. If you want to park at Tregaron and cycle in, that is a great option, although you had better have legs fit for hill climbing. There are some steep 16-20% on the way.

AllTrails lists several walking routes, and there’s a QR code on the information board at the dam. Twice I’ve tried it; twice it hasn’t worked. Signal here is more wishful thinking than reality.

Crossing the dam however gives you access to a long gravel road on the far side, suitable for walking or mountain biking. It feels wonderfully remote.

Gwenffrwd‑Dinas: More Than a Nature Reserve

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A short drive from Llyn Brianne is the RSPB reserve Gwenffrwd‑Dinas. AllTrails has a 10.8 km circular route here, and I do wonder if it’s the same as the elusive 11 km QR‑code walk.

This trail includes Twm Sion Cati’s Cave — hideout of a 16th‑century highwayman. The cave walk is about 2 miles long. The board says 90 minutes; I usually scoff at timings like that, but today I came in at 80 minutes.

Bring binoculars. Alongside the usual tit flocks, nuthatches and woodpeckers, I saw a spotted flycatcher. No dippers or grey wagtails this time.

A Walk Through Several Movies

The walk begins on a boardwalk crossing a stream filled with plants that look straight out of Jurassic Park. I half expected a pack of Compies to appear. You hear the river before you see it, and despite the recent dry spell, it was charging down the valley with real urgency.

This is the Afon Tywi — Wales’ longest river — heading with gusto towards Carmarthen Bay. It tumbles over huge boulders of Silurian shales and mudstones deposited during the last Ice Age.

On the opposite side, the slopes are cloaked in ancient woodland: sessile oak, birch, alder. A true Celtic rainforest, rich with mosses and lichens that give the whole place a Lord of the Rings atmosphere.

Once you leave the boardwalk, the path becomes more challenging — exposed roots, rocks, and a steep ascent with twists, turns, and stepped sections leading to Twm Sion Cati’s cave. It’s an open‑roofed cave requiring a bit of scrambling but is absolutely worth it.

Twm Sion Cati — real name Thomas Jones — was born in Tregaron and lived a double life: aristocrat by day, highwayman by night. After gaining wealth, he married, bought a royal pardon, and eventually became a mayor and magistrate. The cave walls are covered in etchings, some modern, some very old, showing just how long visitors have been drawn here.

After descending from the cave, the path widens and meanders through forest before rejoining the boardwalk.

It’s a beautiful walk — but again, no facilities. Hopefully you’ve saved enough picnic to enjoy back at the car park.

To avoid the narrow roads back to Tregaron, you can continue on to Llandovery (about 11 miles) and take more main roads back towards Aberystwyth.

Another day, another corner of Wales that feels ancient, cinematic, and quietly extraordinary.