Erwtomau/Rhiwrugos is probably the largest mine of the Rheidol United mines, and ascends up the Nant Rhugos ravine from the bottom to the top. The deep adit, blocked, used to lead in between two masonry retaining walls on top of long tips above the Afon Rheidol. It's easy to access over a fence from the path above, though it isn't very interesting here. Take care for the ground is wet and boggy. A tramway as well as a leat led from it to the dressing floors a few hundred yards to the West.
An interesting thing has happened near this adit - a tree, visible from the path above, has grown around a piece of railway track! It sticks out from both sides of the trunk, showing that tracks had once been nearby. Further up the ravine where the railway crosses the stream on a high inbankment, the tips from the upper adit and dressing floors can be seen above. Although named this, this isn't actually the highest adit by far. A path passes through the site, and the concrete buildins suggest more recent working than the old stone ones against the hillside. A few yards along a narrow path around the hillside, the wet upper adit is reached. The tunnel is suitable for any walker by for the water level is shallow. Drill holes in the spacious tunnel can be seen but take care as you near to a first stope of some 150 feet deep. It's hard to tell if your on a false floor or not but looking a little to the left a hole in the wooden flooring is dangerously visible. Beyond, a tunnel leads East along the stope with wooden roof supports as seen wedged in the stope above and below. A further drift leads West along the stope and doesn't look inviting. Along it are one of the most spectacular stopes I've ever seen - the top of it is visible after emerging from the deads piled on timbers near an old ladder. Working platforms can be traced all the way up to the top of the stope. Modern workings can be reached beyond which lead towards the adjacent Gwaith Coch middle adit which is unfortunately blocked. If not, this would make an amazing round trip!
Crossing the stope the main adit leads on through shallow water and to a further, less obveous stope until you're right up to it. The stope leads only right (West) and an alcove lays on the left. This one is safer for I'm convinced that the adit doesn't actually cross the stope but go past it to the side. The impressive wooden supports here are plentyfull and a platform can be seen further up the larger stope. A drift leads West here too and an incline to a lower level which probably connects to the lower adit.
The main tunnel dries up after a bit and stops dead after a pile of deads as if the workers hadn't bothered to take it to the tip once abandoning this level.
From a stile back on the site of the dressing floors, an overgrown worker's path from Nantglas mine leads into the heart of the ravine. After a bit of scrambling, a dry and scienic level is reached, portal partly blocked. It soon leads via a sharp nearly 90 degrees turn to a very deep winze and ends.
Along a short path through a rock cutting on one side, Nant Rhugos stream on the other, a large flooded level is reached on a grassy ledge beside the waterfall. It leads through water untill drying up a bit after a few curves.
Up at the head of the ravine are shallow open cuts near the scienic path, and deep open stopes following. Under the workings two adits lead, one being an ancient coffin-level and the other partly blocked and not currently accessible. This mine was one of the oldest in the county and the coffin-level shows this. A tiny resevoir lays in the nearby field under the A4120 to Devil's Bridge.