If you keep your eyes peeled along the A4212, between Capel Celyn and Trawsfynydd, you may have just caught a glimpse or two of a beautiful old rail bridge linking a couple of hillsides in the Snowdonian countryside together. This marvel of 19th engineering is the Cwm Prysor viaduct - a train bridge that carried passengers and cargo through the beautiful surroundings for around 80 years before its retirement. The old line has long since gone, and the former route is now far too aquatic to be recreated thanks to Llyn Celyn, but this just provides a great opportunity for adventurers to take a tour of a grand piece of architecture that could have very easily been overlooked otherwise. This one can be a bit of a quick stop if you want to, or a grander adventure across the landscape, following the former route of the Bala and Festiniog railway as far as you are able. Let's get walking...
Finding a good view of the viaduct from the road isn't easy, with little places to pull over along the A4212 and dense foliage interrupting the sightlines. You can try pulling up on the verges to get a look, but please be respectful of the locals and other road users. The start of the walk begins at a small lay-by off of the A4212 near Llyn Tryweryn right here - other than the lake there isn't much to navigate by and it looks like pretty much any other lay-by so if you are heading west from Capel Celyn then pass the little lake and keep an eye out on your right for where to pull in. If you are heading east it is a little trickier, you will pass the entrance to a farm on your left before ascending a fairly long hill, the lay-by will be near the crest of the hill on the left. The entrance to the walk itself is a little tucked away from the road but will be more visible to travellers heading from the west, it has a vehicle gate (open on our visit) and a ladder stile to allow pedestrian access at all times. Parking is a little limited, even if you are unlikely to see more than 1 or 2 other cars there at any time, but still, try to park in a way that allows other visitors to get on too. Public transport is unlikely to get you any closer than Trawsfynydd, but for those of you who love a good walk then there might be an option for you - the extended walk discussed a little later on and shown on the map above will take you almost all of the way to and from Trawsfynydd, so if you don't mind the extra 4 or so miles (one way) then this is an option.
From the car park you have a short walk to Cwm Prysor viaduct, firstly along a stony path that eventually turns to a proper farmers track, little more than two tyre tracks carved into the muddy ground. The first bit is easy-going and has spectacular views out up the valley, well worth stopping off to grab a photo even if you don't plan to do the viaduct walk. Otherwise, continue along the path until it turns off up into the woodlands - ignore the path and continue straight ahead onto the farm track mentioned previously. From here you are likely to find the situation get a bit boggy, with many pools filling the ruts carved into the ground. It is cool to see how the old train line had been excavated from the hillside to keep the grade of the track as easy as possible, following former tracks is a great way to travel if you are looking for the easiest going route and this is no exception. One of the most interesting parts of this sodden walk is all of the wildlife you can see, we spent absolutely ages bounding from puddle to puddle, watching the huge number of tadpoles and even the occasional newt darting around enjoying their shady piece of the earth - an entire ecosystem enclosed in a little stretch of path that is just so fascinating to watch.
If you can pull yourself away from amphibian spotting and get some walking done then it won't be long before the trees drop away as the path opens up a bit and the walls that line Cwm Prysor viaduct pop into view. The right of way restricts you to the path you are currently walking on, but there are a few spots along the way where you might be able to catch a better view of the viaduct, just be careful of the uneven terrain, ruts and hidden streams and be respectful of the fences so you don't venture too far onto private property. There are small gaps at either end of the viaduct that allow little glimpses of the face of those marvellous arches so be sure to carefully check those out before venturing onto the deck of the bridge.
On our visit to Cwm Prysor viaduct, the clatter of wheels on track and throb of engines had been replaced with skittish sheep bleating their warnings at us. The windswept top of the viaduct is now a grass patch, with only a few markers alluding to its former glory, but the views make me happy people are still able to access this wonder. A small stream carves its way between the woodlands and passes through the grand arches of the viaduct to travel out over the farmland beyond, a wonderfully serene place that can really take your breath away.
The viaduct was constructed in the late 19th century and formed part of the link between Trawsfynydd and Bala, with a handful of smaller halts in between. The viaduct carried passenger trains without incident until the line went out of operation in 1960, its track would be lifted but the viaduct itself is now a Grade II listed structure. Most of the path of the line heading west from the viaduct is still visible from above, and some of the platforms still exist to this day (although a lot of the halts have been lost to time). From the lay-by where you parked, the route would have continued east following the modern road path, and the farmhouse a short way past Llyn Tryweryn would have been the Cwm Prysor Halt railway station. Beyond here the old route passes through Arenig before arriving at Capel Celyn, a name that may be familiar to the local history fans out there; not only was the old railway route flooded by the construction of Llyn Celyn but controversially the community of Capel Celyn too - controversial because the Welsh had no say in the construction of the reservoir, Liverpool was granted planning consent via an act of parliament and Welsh opposition was completely ignored (the history of reservoirs in Wales is a fascinating one well worth reading into, and unfortunately repeats itself often).
I was aware and was potentially planning, depending on how the time went, to explore much further beyond Cwm Prysor Viaduct but the May weather had other plans. We visited on a dry day, and what had been a reasonably dry spring but even still everywhere was soaked - more than likely the natural runoff from the hillside drains down to fill the old train line keeping it wet for longer. As mentioned above, the path to the viaduct was full of pools but it was the path immediately after the bridge that became impassable. An absolute quagmire that our boots were simply not able to cross, we would have required wellies to stand a chance of not sinking into the bog and losing a shoe. If you fare better by visiting in a drier season or have the footwear for the conditions then there is a great opportunity to explore here - the route, as shown on the map above, is meant to lead almost all of the way to Trawsfynydd (it appears to end around here where it joins up with a single track lane, the rest of the train line is visible from above but does not seem to be accessible). It should be an exciting route, it twists its way along the hillside on its carved-in little ledge before gently descending towards the town - giving amazing views while you venture onwards. I have included some marks on the map of places I wished to explore, including some of the old railway stations along the line and a smaller, but still charming, rail bridge over another stream. It is a shame we were unable to travel onwards, but this will just have to be an adventure for another day, and believe me when I say that seeing the viaduct alone was well worth the quick stop off.
Hopefully, this little taste of the adventure on offer at Cwm Prysor viaduct has left you tempted to take to the trails yourself, especially to complete the extended walk we were unable to. There are three great opportunities here for all skill levels, those who just want a beautiful view can drop into the lay-by, snag some awe-inspiring photos and continue onwards. If you have a bit of time to spare then you should make that short walk to check out the viaduct and the additional views it offers, but if you have some time for a real adventure then walking as much of the line as is accessible definitely sounds appealing to me! Everything from a quick stop to the potential for a full day out. You could even continue on down the lanes after following the train line to check out Llyn Trawsfynydd and keep walking to your heart's content. There is the recipe here for a grand old day out, I am sure you could merge Cwm Prysor into whatever other plans you have as a perfect addition.