Including Pwll Crochan/Clydach Lower Waterfall, Pistyll Mawr/Coal Tar Cave Resurgence Waterfall, Cwm Nantmelyn Waterfall, Waterfall Cave Resurgence Waterfall, Ogof Clogwyn, Devil's Waterfall/Pwll Cwn, Pwll Rhys.
The Clydach Gorge is a strange cross between wild gorge, and urban/industrial influence. There are many paths, but most are not really designed for countryside walks, and are better as utility footpaths for local residents. As a result, there are no convenient routes that take you easily from waterfall to waterfall; if this route seems a little disjointed as a result, that's because it is. The urban influence, however, means that almost all waterfalls have a convenient parking space nearby. As this is intended to be a walking guide, it will offer three parking options with a looping route. I would recommend the Clydach South (Danycoed) parking option, as it means the walk ends downhill, and offers interesting industrial remains to look at afterwards.
From Cardiff, take the A470 to the end of Merthyr Tydfil. From Merthyr Tydfil, take the A465 towards Abergavenny, follow it past Brynmawr, and down the Clydach Gorge. At the bottom are the first side roads since Brynmawr, one on the left, and then one on the right. For the Drum & Monkey pub parking, take the one on the left, and follow it back up the valley for 2 km, to the car park down a steep road just after the pub on the left. SO 2152 1257. For the Clydach South and Gellifelen parking, take the road on the right. It swings left and climbs to a junction. Turn right, and continue to a fork. For Clydach South parking, take the right fork, and find somewhere convenient to park, preferably near the end of the road, where there is a small parking area. SO 2263 1279. For Gellifelen parking, take the left fork, and follow it uphill, crossing a dismantled railway. When the road hairpins around to the left, continue ahead, around a hairpin to the right, to a junction. Aim down to the right, take the first left, and drop down to a parking area beside some railway tunnels. SO 2149 1213.
From Clydach South, take the footpath at the end of the road through the village (where you should be parked), and follow it up the valley. Early on it appears to split (take the left branch), but remains level until it reaches a junction with a steep tramroad on the left. Continue ahead to a set of powerful cascades, and then the lower Clydach waterfall (traditionally Pwll Crochan). Return to the steep tramroad, and follow it up until it reaches a road beside some lime kilns, and a dismantled railway line. Follow the road up onto the railway line, then take the railway line to the right. Follow it around a long curve (which has several small waterfalls in wet weather on the left side of the cutting) to an embankment and some tunnels, where a stream down to the left has a small cascade. Either go through the right tunnel (you will need a torch), or follow the path around to the right, staying level when it joins a road, to the other end of the tunnels. This is the Gellifelen parking area, where a small waterfall is up beside the tunnels, at the outflow of an adit.
From Gellifelen, there are two detours that may be of interest. The first is 4-5 km long and takes in a few interesting waterfalls. The second is quite short, and takes in three waterfalls. The first detour is to follow the right bank of the continuing dismantled railway line, staying with it as it passes some houses, and continues for 2 km to the roundabout at Brynmawr. From there, turn right and head down the verge on the right side of the Clydach Gorge. Not far down, there is a parking space where you can hop over the fence to see the waterfall at the pothole entrance to the atificial Coal Tar Cave. Staying on the other side of the fence, a little further downstream is the resurgence adit, with an impressive 10 metre spout waterfall above it (traditionally Pistyll Mawr). (The tops of these may be visible from the railway line, but cliffs make it too risky to descend directly from there.) Return to the other side of the fence.
Go back up to the roundabout, cross the road to the left, go under the roundabout through the pedestrian subway, and take the path to the right on the other side. (Warning; the path sometimes suffers from overflowing sewage, usually only after very heavy rain.) An elevated pipeline starts with a small cascade behind it. Just before the pipeline ends, a side stream on the left, Cwm Nantmelyn, also has a small cascade, and a small path beside it quickly leads to a much bigger waterfall. Follow the main path to a subway that takes you under the road. On the other side, steps to the right lead to a path that heads up the side of the gorge. If water levels are high (particularly in winter), take a small detour; follow the pavement down the valley from the subway for another 300 metres to see another inlet waterfall on the left (just after a staircase on the right), then return to the path. Follow the path up to the dismantled railway line again, and turn left to return to Gellifelen.
The second detour is to take a path that heads down into the gorge, just past the first building on the way along the dismantled railway line. This leads to a junction of paths in the beachwoods. Turn left then immediately right down the wooden steps. On the other side of the gorge is the Waterfall Cave resurgence waterfall - best seen in winter when there is less foliage. The path leads directly to Ogof Clogwyn, with a short waterfall dropping from its main entrance. A further cascading waterfall can be seen in the main river, just upstream. Return to Gellifelen.
Once you are finished with the detours, head along the road away from the railway line and tunnels, taking the left branch when the road forks. After a short distance is a rootpath on the left. Follow it down a very steep route beside a stream gully, to the bottom of the gorge (to the left is a path to Pwll y Cwm, a major cave resurgence). The path crosses the Devil's Bridge, over the top of the Devil's Waterfall (traditionally Pwll Cwn), the largest and most powerful waterfall in the valley. The bridge is the best viewpoint - there is no safe way to access it from below. Cross the bridge, and follow the path up to a subway. Go through it, and up to the Drum & Monkey car park. A good place to stop for refreshments.
From the Drum & Monkey, head up out of the car park, and take the road to the right. Follow the road for a while, passing some lime kilns on the left. Stay on the road until you reach a stepped path on the right (there is a sloping path on the right a little before this, and in theory that can be used instead, but it was blocked on my last visit). Take the stepped path down to a back lane. Follow it to the left, and continue for 1 km, until it attempts to join the larger road again. Just before this, take a road down to the right, then a path to the left. This leads over a bridge, back into the Clydach South housing estate. (To the right is a footpath that leads behind the houses, back to the parking area.)
Now back in Clydach South, follow the road back out of the estate, and just before some playing fields on the left is a path down to the Clydach Ironworks - the destination for the minerals prepared in the lime kilns, and transported down the tramroads. Cross the bridge over the river at the iron works, turn right, and take a subway under the main road. Follow the path up to a smaller road (the same road as the Drum & Monkey is on), and follow it down to the right. As the road swings right to join the main road, take a smaller road ahead. When it forks, take the right branch. Just before it crosses the river, take a footpath on the left, which follows a narrow path tucked behind some houses. This leads to a powerful waterfall, Pwll Rhys (aka. Pwll-y-Rhechu/Rhychu). Return to Clydach South (an alternative route back is to cross the bridge above the waterfall, and follow the pavement along the side of the main road, back up to the road by the subway).
Whilst every care has been taken in the compilation of this description, neither the author nor his fellow walkers can accept responsibility for loss or injury arising from any errors, omissions or inaccuracies in this description. You follow this description at your own risk.