The Cwm Prysor viaduct, a marvel of Victorian engineering that still stands tall 122 years after its construction, is an impressive sight for those traveling along the A4212 in Eryri (Snowdonia). Despite its grand look, it is nestled in a sparsely populated area of the national park and often overlooked. While other rail crossings in North Wales receive their fair share of attention, the Cwm Prysor Viaduct has quietly faded into obscurity.
However, its nine elegant arches are a popular feature on many walking wish lists. Despite being relatively close to the main road between Capel Celyn and Trawsfynydd, reaching the viaduct can be a challenge. But those who make the effort are rewarded with breathtaking views down the valley and towards the Arenig and Rhinog mountains.
For a quick visit, many choose to park at a forestry layby near Llyn Tryweryn, from where it’s just over half a mile walk to the viaduct. As the former route of the Bala and Ffestiniog Railway, longer treks are also possible, North Wales Live reported. A grassed permissive path runs over the viaduct, and a courtesy path runs 5.5 miles down to Trawsfynydd, offering encounters with dramatic hillside cuttings, charming stone bridges, and abundant birdlife.
Spanning 450ft across the valley and seemingly clenching the surrounding hillsides is the impressive viaduct. The Afon Prysor river, flowing beneath the structure’s central span, varies dramatically with the seasons from a mere trickle to a raging torrent. According to Coflein, Wales’ historical records body, the viaduct is described as “curving and dramatic.” It’s been over half a century since the old railway line that used to run across the viaduct was dismantled in 1961, just a few years after British Railways swapped its original stone battlements for concrete and railings.
This very sense of danger was utilised by television directors for S4Cs 2018 thriller series ‘Hidden’ (Craith), featuring the viaduct and its formidable 105ft height as the location for a critical suicide scene. The viaduct was initially constructed for the Blaenau Ffestiniog slate quarries. It stretched 22 miles to connect far-flung communities that had no road access until the emergence of the A4212 during the early 60s.
Despite its importance, the line saw dwindling usage: as of 1957, only about three passengers disembarked daily at the remote Cwm Prysor halt. Often referred to as the Blaen-y-Cwm Viaduct, this landmark garnered grade II listing in 2004. It serves as a bittersweet memorial to the lost community of Capel Celyn, which vanished beneath the waters upon the creation of the Llyn Celyn reservoir following the flooding of Afon Tryweryn valley.
In 1961, a difficult decision was made: a short section of the railway near the newly formed Llyn Celyn would be submerged. With diminishing train income, opting for a deviation was disregarded, leading to the preference to reallocate those funds into constructing a new road. January 27, 1961, marked the end of an era with the passage of the last freight service. Traces of the historical railway are still visible alongside Llyn Celyn’s southern shores, stirring the imaginations of railway heritage supporters.
Yet the financial hurdle to create a bypass and lay down new tracks is daunting, suggesting that trains might never again traverse the Cwm Prysor Viaduct. But there may be a flicker of hope for the railway’s future. A heritage group established in 2019 has its sights on resurrecting the railway, albeit for a modest stretch between Blaenau Ffestiniog and Trawsfynydd Lake Halt, aiming to leverage it for heritage tourism on a standard gauge track.
The project has been charted out over a decade with a projected cost of £18 million to restore merely 6.5 miles of the line, as new structures have emerged upon parts of the former track further along. The task ahead is monumental not only does the track need to be recovered, but four new stations must be built and two others need refurbishing or altering. Plans are also in place for a heritage railway center.
After Covid restrictions eased, volunteers began clearing sections of the line that had become overgrown with vegetation. In contrast, Cwm Prysor Viaduct and the remaining line to Bala will remain beautifully isolated. The stunning crossing, once an imposition on the landscape, has now seamlessly integrated into it. From afar, it seems content to fade into the backdrop against the grandeur of the surrounding mountains.