The Hollow Mountain
The mountains west of Ffestiniog are relics of Snowdonia’s once mighty slate industry, riddled with old mines and quarries. As well as bagging summits, intrepid walkers can also venture underground, deep into the very mountains themselves. Grab your headt
Discover a secret world through the tunnels and mines of the abandoned Snowdonian slate industry
First, here’s a seemingly simple question to ponder. Why do you love the mountains? Everyone’s answer will likely be personal and unique. After all, we climb and walk in the hills for different reasons. For me, it’s their sheer, awe-inspiring presence. A very big landscape can make you feel very small indeed. Mountains are humbling, in a good way. But they also feel reassuringly solid. Rock-solid, in fact.
In certain places, however, you come to realise that sensation is a myth, pure fallacy. What we like to think of as honest, solid rock is as riddled with holes and fissures as the woodworm-infested beams of an old house. Because the thing about rock is that it hides secrets – valuable secrets. Over the centuries, our mountains have been mercilessly exploited. Precious ores and metals, even the very rock itself, have all been quarried, mined and extracted from the hillsides, leaving behind an intricate network of tunnels, caverns, mines and shafts.
The search for slate
Nowhere is this more evident than in the hills and mountains of Snowdonia, an area that has been quarried for centuries to obtain tin, copper, lead, zinc, iron and even gold. But what shaped the landscape more than anything else was the search for slate. It was once said that Welsh slate roofed the world, such was the vast scale and might of this industry at its height. The Victorians exported it across the British Empire and beyond, all the way from Iceland to New Zealand. And though the slate industry declined dramatically by the mid-20th century, the remnants of this formerly grand global enterprise are still writ large on the landscape of north Wales.
Some consider it a scar, an eyesore. That was certainly the case when the boundaries of the Snowdonia National
Park were drawn up in 1950. One place in particular bore the brunt of this disdain: Blaenau Ffestiniog, the one-time slate capital of the world. Back then, the National Park Commission did not consider Blaenau to ‘satisfy the criteria of exceptional scenic beauty’.
It meant that the town and its surrounding hills were omitted: disqualified from being part of the national park for their looks, the ugly sister that didn’t get invited to the party. Blaenau was a literal blot on the map. Even today, the OS Landranger series depicts it as a strange, yellow-fringed island in the middle of Snowdonia.
It all seems a bit unfair. But there’s no denying that the slate industry made a mess. Even the language of the slate quarries is ugly – the waste rock is known as ‘spoil’, and the spoil that cascaded down the mountainside are ‘tips’. Blaenau suffered more than most, despite the fact that most of its quarries weren’t the open, terraced workings found elsewhere in north Wales. Blaenau’s quarries were more accurately mines, worked underground via openings or chambers, all supported by giant pillars of solid slate. Some were more than 1500ft deep, requiring a mass of men and machinery to haul the slate blocks to the surface. Compressed air equipment was needed for drilling, dynamite and gunpowder for blasting, miles of rail- and tramways to move the slate, vast mills and enormous saw tables to split and dress the stone, and huge pumps worked all day long to keep the mines clear of water. The remains of this herculean subterranean enterprise are still there. Which means that if you’re looking for hollow mountains, Blaenau is where to find them. Going underground
The town was eerily quiet as I drove through it in the early hours of the morning, en route to a pre-arranged rendezvous with Trail photographer Tom at the head of Tanygrisiau Reservoir. The day before we’d planned a mountain circuit that would venture up into the Moelwynion via the Stwlan dam, climbing the broad Craigysgafn ridge before descending to explore some of the disused Ffestiniog quarries. And though we were planning to knock off two decent peaks, for once the day’s objectives weren’t just going to be lofty summits. We were also hoping to venture into some of the old tunnels, chambers and passages that fracture these mountains. The prospect filled me with anticipation, but also with a little nervousness. I was a hillwalker, sure, a climber, perhaps, but a caver most certainly not. Being 6ft 4ins also meant the thought of too many cramped and confined spaces filled me with a slight sense of unease. As I mused on this, I realised something else: I’d forgotten to pack a headtorch.
The winding access track up to the Stwlan reservoir is the stuff of a Top Gear producer’s dream, or a road cyclist’s nightmare: a narrow mountain road with six hairpin bends that climbs some 900ft in under 2 miles. The average gradient is 9.61%, enough to test the lungs and calves of even a seasoned Tour de France grimpeur. It’s a testing start to a day in the hills too, but also offers impressive views of the slate quarries and tips that surround Blaenau: grey and purple-hued cascades of rock that seem to tumble straight down into the town. Some find it bleak and forbidding, a little overbearing, even ominous. I turned to Tom and asked him whether he thought the scene was ugly or beautiful. He smiled. “It has an ugly beauty,” he replied, with the eye of a veteran photographer and the tact of a seasoned Snowdonia hillwalker.
Ugly beauty: the same phrase might be said of the hulking dam that holds back the waters of Llyn Stwlan, its impassive concrete buttresses jarring with the mirrored surface of the lake, placidly reflecting the surrounding hills. From here we tacked left up the shoulder of Moelwyn Bach, initially making straight for the summit before being diverted by a dark cleft in the hillside that, on closer investigation, turned out to be a shallow cave. It gave us our first chance to venture at least a little way underground, a taster of what was to come.
The mountain’s airy summit was a sharp contrast, reached after an easy scramble and a little rock-hopping in order to pass a small, rainwater-fed llyn. So too was the descent to the bwlch that separates the outlier from its bigger sister, Moelwyn Mawr, and the climb up the broad ridge towards the main peak’s squat trig pillar, which involves crossing
“IT WAS ONCE SAID THAT WELSH SLATE ROOFED THE WORLD, SUCH WAS THE VAST SCALE AND MIGHT OF THIS INDUSTRY”
a striking band of white quartz. This unusual geological feature is a trait that north Wales shares with the Alps, which is why these bands are known as Alpine fissure-veins. Coincidentally, they were also formed by the same metamorphic processes that created the slate here. Canny quarrymen soon worked out that wherever there was quartz, there was likely to be good slate nearby.
Here, there certainly was – and plenty of it. Inevitably, what came out of the Ffestiniog quarries was also used to build the surface workings. As such, these hills are dotted with the remains of abandoned inclines, huts, houses, barracks, mills, smithies, chapels and other buildings, all constructed from slate – though much more is now gone, demolished when the quarries closed. Among the grey sentinels that still survive, there are also rusting old engines, wagons and machinery scattered across the high mountain plateau. It all hove into view as we walked down the northern flanks of Moelwyn Mawr. Picking our way amongst this deserted, derelict memorial to a once-mighty industry was a strange, eerie experience.
Cave spiders
It got stranger when we spotted a dark, dank entrance to a passage that led off underground. In mining language, this was an adit: an open, slightly sloped entrance that leads from the surface to the interior of a mine. It’s distinct from a tunnel, which connects two underground chambers; and a shaft, which descends vertically into the earth. Tom fished a headtorch from the lid of his rucksack and handed it to me, before grabbing his camera and ducking into the gloom. I started to follow, adjusting the beam of the headtorch with one hand and gingerly feeling my way along the dripping walls with the other, until Tom helpfully mentioned something about cave spiders.
Surprisingly, we soon emerged, blinking and somewhat confused, into daylight again, finding ourselves on a ledge at the edge of a vast open pit. I realised that this was Rhosydd Quarry’s West Twll (simply, ‘hole’ in Welsh), the oldest part of the site, begun in the 1840s and gradually enlarged over the years to a depth of over 200ft. As the workings went deeper, adits and tunnels were driven north in search of more slate. The open quarry then developed into a mine, as it followed the vein of slate ever further northwards – and downwards. Rhosydd was considered a medium-sized slate mine by Ffestiniog standards, a bit-part player compared to the colossal Llechwedd or Oakeley Quarries, but it still consisted of 14 underground levels, with a total of 170 chambers from which the slate was mined, or ‘won’. The lower levels are now flooded, but cavers – real ones that is, with climbing gear, helmets, harnesses and shiny PU-coated drysuits – have explored the remaining levels, which can apparently be accessed via the level 9 adit, an incredible 677m-long passage that takes you straight into the heart of the mine.
As we gazed into the depths of the pit, a walker appeared across the chasm, making her way along its farthest rim, walking poles clacking against the slate spoil. She glanced down and then turned back to call to an unseen companion over her shoulder. “Oh, it must be an old quarry or something,” she said, nonchalantly. Tom and I looked at each other in silent disbelief. It seemed incredible that anybody could hike into these hills without at least a passing familiarity with the slate industry that shaped them. Emboldened by our first foray, we retraced our steps and headed for Wrysgan, another disused quarry that lies literally on the side of a mountain, chiselled somewhat inaccessibly out of the side of Moel-yr-hydd. Like most of the slate mines in Blaenau, Wrysgan was excavated as a series of chambers, with pillars of rock left between them to support the mountain above. Most of the adits to these chambers, and the tunnels linking them, are still open. With a new taste for the subterranean, we delved into them, marvelling at the sheer size of these underground caverns. I later learned that some of the chambers at Wrysgan are exceptionally wide, even by north Wales standards, measuring some 40m across, with only 15m of rock left between them to support the mass of mountain above. I’m glad we didn’t know that rather sobering fact at the time. The day was already waning, so we studied the map to check our return route. The quickest, steepest and arguably most treacherous way back down to Tanygrisiau from Wrysgan is via the quarry’s most obvious surviving feature: the main incline, which was completed in 1872 to connect with the Ffestiniog Railway some 625ft below. At its summit, it drops sharply down the hillside via a tunnel in the rock, which was bored straight through the ridge that divides the quarry from the valley below. With a little energy left in our legs, we decided to brave the descent. And as I clambered gratefully down the tunnel towards an archway of pure white light, I imagined I felt a little like those exhausted Victorian quarrymen, returning to the surface after a long day spent deep in the bowels of the Earth.