Croesor Slate Mine
Location
Description
The underground world of Snowdonia is colossal. You don’t need to look very hard once you enter the town of Blaenau Ffestiniog to see just how much work has gone on over the years – although by now all evidence of human activity has morphed into the landscape and you might be forgiven for not noticing straight away.
On the outskirts of the town, you’ll find the Cwmorthin Valley (not an official name) containing Llyn Cwmorthin, the Cwmorthin Waterfalls and Cwmorthin Slate Quarry. It’s a beautiful walk through the wilderness and I would encourage even non-mine exploreres to take a trip there. You can walk right past the Cwmorthin Mine adit entrance and take a look through the locked gate.
This is where you can take a guided trip into the underground world, courtesy of Go Below who are based in Betws-y-Coed and Tanygrisiau. If you want fancy a one-off adventure or simple seek a taste of the underground world then I would highly recommend one of their trips. The mines of Cwmorthin currently offer the world’s deepest underground “hotel” experience amongst other things.
However we must continue past Cwmorthin and walk up the steep hillside and into the next big slate quarry – Rhosydd. This is the other half of the great underground adventure that connects to Croesor mine, and I will details more about it in its own page.
To reach Croesor, you must continue through Rhosydd and walk through the hills for approximately half a kilometer. The village of Croesor lies on the other side of the huge valley at the bottom of the abandoned Croesor tramway – the old railroad that would have been used for transportation from the mine. The remains are now just a simple off-road track, and you can drive up to the mine from the other end in the correct vehicle. (I would refrain from attempting this in the winter though, a slip in the wrong place might send you tumbling down the steep slopes – quite possibly to an early death).
You’ll know you’ve reached the outer workings of Croesor Quarry when you spot the large area of flat ground on the edge of the slopes. Numerous old ruins remain, with the adit entrance hidden between them.
Once you’ve climbed through the small entrance, you’ll find yourself in the long and spacious tunnel. It’s a pretty decent length – perhaps around 200m – but nothing compared to the nearly 700m long entrance tunnel found at Rhosydd. There isn’t much to see along here beyond the air shafts which pop out into the hills above at numerous points.
At the end of the tunnel, the area suddenly expands into what would have been an old sorting area for the mine carts. In front of this is where you’ll find the main slope shaft – with the levels going further below now completely flooded. The primary continuation for the Croesor-Rhosydd trip is up the slope shaft.
Between the upper and lower slope shaft is where you can see the remains of the old hauling winch, although this one is in pretty poor condition and much better examples can be found further in the mine.
To the right, you can walk up to the first of many great chambers – this one also flooded. The mine does continue across the chamber although I haven’t yet taken by dinghy across to explore.
To continue up the slope shaft and venture deeper into the mine from this point is only possible for properly-equipped explorers. Although multiple routes exist, you will soon find the need to either descend down ropes or traverse across steep chamber edges.
You should NOT continue up the slope shaft from the intitial entrance floor without the appropriate equipment.
