Pont-sarn to Morlais Castle – Waterfalls, Dippers, and a Journey Through History

Pont-Sarn Viaduct

Pont-sarn, near Merthyr Tydfil, lies on the Taff Trail. It is one of those places that quietly steals into your affections. The morning light found me standing by the Taf Fechan river, its cool, clear water tumbling over the Pont-sarn Waterfall in a frothy white curtain. The sound here is constant but soothing, the kind of backdrop that makes you want to slow your pace and simply watch the water carve its way through the rocks.

Pont-sarn Waterfall and the Bluepool (Pwll Glas)

The view of the Pont-sarn Waterfall and plunge pool from above.

After taking some long exposure photographs with my cameras, I took to the air—well, my drone did. From above, the great sweep of the Pont-sarn Viaduct filled my screen, its graceful arches striding across the valley as they have for over 150 years. Built in 1866, the viaduct was part of the Brecon and Merthyr Railway, a vital link for transporting coal and iron through the heart of industrial South Wales. Now, no trains cross its 15 lofty arches, but it remains an impressive monument to Victorian engineering, a reminder of a time when steam and steel reshaped these valleys.

Pont-sarn Viaduct

After the aerial interlude, I walked beneath the viaduct, craning my neck to appreciate the sheer height of its stonework. A shaded trail led me alongside the Taf Fechan, weaving through a wooded corridor where the air was rich with birdsong and the smell of damp earth. It was here I spotted my first Dipper of the day, bobbing on a rock midstream before vanishing under the water in search of insect larvae. Watching these remarkable little birds always feels like being let in on a secret—they thrive in these fast-flowing rivers, perfectly adapted to the life aquatic.

Bridge across the Taff Fechan

The path eventually brought me to a small wooden bridge, leading me across the water to join the Taff Trail. This long-distance route threads its way from Brecon to Cardiff, but I was only walking a small section today. My route began to climb, skirting the edge of a disused quarry where the views suddenly opened up over the surrounding hills.

Morlais Castle

Quarries border the Castle's western edge. Morlais Golf Course is situated on its eastern side.

Higher still, amid the whisper of wind through grass, the remains of Morlais Castle came into view. Built in the late 13th century by Gilbert de Clare, the powerful Earl of Gloucester, the castle was part of a bitter territorial dispute with Humphrey de Bohun, the Earl of Hereford. Their feud eventually led to the Battle of Maes Moydog in 1295, though Morlais itself saw little in the way of completed construction—much of what stands today is the bare bones of an unfinished fortress. Still, the rough stone walls and earthworks speak of a turbulent era, when such strongholds were as much statements of power as they were defensive structures.

You can see Pen-y-fan and Corn Ddu from the castle.

Beneath the castle ruins lies its most atmospheric remnant—the crypt. Cool and dim, with vaulted stonework still clinging to the shape of the chamber, it offers a rare glimpse into the medieval underworld of the site. Though its exact purpose is debated, some believe it served as a storage cellar, while others speculate it may have been a chapel or burial chamber. Standing within its shadowy confines, you can feel the centuries pressing in—the air thick with the scent of damp stone, and the knowledge that this place has outlasted everything built above it.

The entrance to the crypt

The stone arches remind me of tree branches - quite gothic.

Standing among the weathered ruins, I thought about the centuries of change these valleys have seen—from medieval skirmishes to the cracking of rocks during the quarrying, thunderous locomotives, the shouts of "Four" ( there is a golf course next to the castle)  and now to quiet trails where Dippers flit and the river flows on, unchanged in its rhythm. 

My walk had been part wildlife ramble, part historical journey, and wholly the kind of day that keeps me wandering these landscapes in search of both.