Make it stand out.

In remote North West Scotland, where­­­­ rock is ancient beyond imagining, sits a curl of much younger limestone. Westwards lie the oldest, hardest rocks on earth. Aquamarine Lewisian Gneiss, stippled and striped with convoluted bands of white, red, and charcoal grey, were birthed in the fiery heart of ancient earth. A billion or more years later desert sands blew across the Archaean landscape, eventually settling and solidifying to form rust-brown and pink Torridonian sandstones. Much more recently ice has also played its part. For two million years the Quaternary ice sheets waxed and waned. Some wanings were subtropical, warmer even than our own Anthropocene. During the waxings mile-high ice scraped and scoured, creating the enigmatic gneiss ‘cnoc and lochan’ landscapes and the fantastical sandstone ramparts of monolithic mountains such as Suilven and Stac Pollaidh. Face west and the land speaks of tumult, of fire and ice. Look east and younger upstart rocks of the Moine Thrust are piled in ripples and waves of height, testament to the slow, enduring grind of tectonic force.

But this narrow stretch of limestone country, surrounded as it is by hard lands and great age, gently tells of warmer times and life-filled seas. This is now a place of softer things – scented grasses, rich soils, and countless springs of sweet, clear water. Summer lingers here even as the autumn gales scurry in; the sward is not rusting but verdant and pricked with tiny stars of late-flowering herbs. And, just as with many other limestone regions in Britain, it is redolent with the stories of people. There are prehistoric chambered cairns, the rubble of houses and walls, old field systems and a Clan MacLeod castle, built more than six hundred years ago.

The ancients were drawn inexorably to limestone territory. About twelve thousand years ago, in the days of the great Wild Woods of the early Holocene, this place would have been easier to clear; its rich soils better for cultivation and grazing animals. For several thousand years people have built their homes and sheltered here. Even now, deer and sheep prefer to sip limestone spring water and nibble its tender herbs and grasses. But limestone possesses one very special secret – hidden within its layered bulk are honeycombs of space where air and water may pass unseen. It is porous and permeable. Limestone claims rainwater as its own and allows passage down cracks and fissures and through its very structure and substance. Inevitably the water moves and gathers, dissolving rock and creating larger hollows and passageways where minerals seep and accumulate. Finally, finding a way to the outer world again, water appears in springs and sumps and the ephemeral streams that rise and fall according to limestone’s whim and rainfall’s fancy. This is how caves are formed – acidic water dissolving limestone at its weakest points, slowly widening clefts and opening crevices, and seeking new routes downwards, pulled always by gravity.

Streams issue from everywhere here. In one special place a valley winds eastwards, overlooked by the ramparts of aptly named Beinn an Fhuarain, ‘Mountain of Springs’. I am following a path here that winds inwards beside a river and leads into the limestone itself. After the grand vistas of wild summits and open coasts the vale becomes a gorge and feels cloistered. Waterfalls sing noisily. There have been a lot of downpours recently. Usually, most rain is absorbed by the ground or seeps down through the valley floor but now everywhere drips and fizzles. Water is emerging magically from within the stones and upwelling through the green turf.

As I walk up the valley, I see the dark crags of the Bone Caves ahead. The rock layers are the colour of Japanese tamahagane steel used in Samurai swords, blended layers of platinum, ash and gunmetal. It is said that sword-smiths know the casting temperature of steel by its colour, and can identify the number of times the metal was forged, welded and folded from its hue and chroma. Geologists can do the same with rock strata. This limestone is testament to the warmth and abundant life of ancient seas, its tri-colour greys tell of subtle differences in formation, morphology, and chemistry.

And yet I am puzzled as I clamber up the steep path and approach the caves. What seemed charcoal blue from below is now a multi-coloured micro-universe. Enormous droplets of water splash down. I pull up my hood to stop them trickling down my back. Everywhere the rocks drip and seep with liquid. Everywhere is covered by a thin, near-microscopic sheen of colour – lichens and mosses in stripes and bands of blue and orange, vivid green and purple, pink, and white. The caves themselves are in a line, their mouths varied in size and shape but all unyielding to the light. The slightly tilted rock is laminated as if sheets of limestone have been placed one on top of the other. Each cave is fronted by a welcome mat of lime green and yellow grass, mown down to fine velvet by sheep and deer, through which narrow trails disappear inside into the darkness.

Now I am sitting at the mouth of the largest cave. It is mid-October and autumn is gilding the hills with gold and copper. Even before the remnants of hurricane Ophelia have arrived in the Highlands the day is fiercely windy. Behind me the cave echoes with voices. I can hear the blind water singing deep inside the cavern. There are no other visitors to the Bone Caves but I am sure I hear the ghosts of people long gone. On the steep slopes across the valley, cloud-shadows race upwards chased hard by gusting winds. They carry the urgent roars of stags and I wonder if it is their echoing bellows I’m hearing.

Many bones have been found inside these caves. In the fine debris were a thousand shards of red deer antlers, and other caves held lynx, arctic fox, brown bear, and wolf remains. I look at my dog as he stares out of the cave mouth watching the deer run below him and wonder if his wolf genes are thrumming. Deeper inside this cavern, which is quickly becoming our shelter as the winds strengthen and rain arrives in vertical silver squalls, were once human bones. Hidden in a rock niche with them was a pin made from a walrus tusk. Such a personal gift for someone once loved, a fragment of other lives hidden for millennia. And, much deeper under the mountain of springs, lies a polar bear skull. Were these remnants placed, washed in by meltwaters, trapped by hunters, or did the living go there to die? There are more questions than artefacts, more speculations than answers. Debate wafts back and forth about how the bones came to be there. But sheltering here out of the wind and rain, one reason sits at the front of my mind.

Some years ago, in a summer of heat, we were caught by an unexpected thunderstorm at the summit of Stac Pollaidh, a few miles distant. Intense heat and calm were replaced in seconds by ice-cold wind and hailstones the size of peanuts. Even the deer were surprised; they flung their tawny-brown bodies against the fox-red and ginger rocks. As we struggled to put on our waterproof clothing in the buffeting gusts, lightning began to strike all around us. The flashes of fierce light were reflected in the deer’s eyes; patches of thin mountain vegetation were scorched. Deafened, we scrambled down. The lightning kept striking all about us; steam hissed up in tall plumes. So, we hid; in a tiny cave, under a great slab of sandstone, along with ten thousand humming bees. The roof and walls of our hideaway rippled with wings. Eventually the storm passed. The thick bee-lining began to shred; slowly, then quickly, the insects streamed out into the clearing air and spread across the purple flowering heather.

Who would not seek sanctuary from such violence in places if they could? The Bone Caves of Inchnadamph would also have provided shelter for animals and humans in times of ice and heat, and when thunderstorms strode the peaks around them.

Our afternoon begins to slip away and we ready ourselves to leave. The weather has worsened, and we put on our modern waterproof clothing as hunter-gatherers would have worn deer skin. I imagine myself dressed with ornamental antlers and then laugh at the thought. In these gusts they would be torn from my head. The path down is steep and slippery in the pouring rain. It loops around the head of the valley and on the opposite side of the boulder-strewn riverbed. Although the rocks are slick and wet, the river waters here are running underground.

We look back up at the crags and they are dark and drab once more. I am blown over a few times by powerful gusts, my feet uncertain, and I wish I was back in the security of the caves. All around me the limestone reflects the worsening storm in myriad greys, but I know of its secret forms; the colours and whispering magic, and its storytelling bones.