There is a popular argument that exploration is dead. Livingstone, Scott, Amundsen, Peary and Bingham have, so the theory goes, got there first. There is nowhere left to discover, no blank spaces left on the map to fill in. But people who believe such things have rarely heard the story of Nanda Devi. Half-imagined and half-created, it is one of the last unknowns.

Nanda Devi is among the world’s highest mountains. Rising 25,640 feet above the already mountainous Sikkim landscape it sits on the border between Tibet and India. Visible from the summer colonial capital of Darjeeling, the peak was long believed to be the British Empire’s tallest. For Hindus it has special significance as one of the 5 sources of the Ganges. Standing solemn and distant the mountain has, since the 1880s, been the subject of constant speculation and mystery. For many it is the true location of Shangri-La. Surrounded by numerous Himalayan peaks, 12 of which exceed 21,000 feet, no human had even made it to the bottom of her slopes by the turn of the 20th century. Imperial expeditions in 1885, 1905, 1925 and 1927 all failed to force a way through. Too holy to be visited by locals, moustachioed Brits were among the only people foolish enough to try. Hugh Routledge, having been rebuffed 3 times in the 1930s, declared it more remote than the North Pole. Reports of the extraordinary wildlife and untouched paradise at the mountain’s foot greatly added to the mountains allure. It became a mythical sanctuary.

Only in 1934 did a human being violate Nanda Devi’s new-found sanctity. The feat, still among the greatest in mountaineering history, was achieved by two British climbers who deliberately eschewed existing mountaineering orthodoxy. Eric Shipton and Bill Tilman spent two seasons accompanied only by a handful of Sherpas living largely off the land. They finally gained access through a gorge of almost horrifying verticality, swinging themselves precariously and sleeping on the exposed rock faces. Throughout the ordeal and in true British fashion they refused to call each other by anything other than their surnames - the other options just seemed ‘too damn silly’. Once inside the Sanctuary, the two climbers revelled in a strange Eden; they startled the large numbers of blue sheep that had hitherto avoided all human contact and spent several nights revelling in the smooth, undulating plains of the valley floor.

The gorge through which Tilman and Shipton picked their way.

Two years later Tilman returned with Nick Odell, soon to excel with Mallory on Everest. This time their goal was Nanda Devi herself. The successful climb set a new world record and for a few scant years Nanda Devi was man’s loftiest achievement.

It was not until China detonated its first atom bomb in 1964 that the mountain would once again return to view. Keen to monitor the Chinese weapons being tested on the Tibetan Plateau, the CIA decided on Nanda Devi as the site for a new surveillance post. Unaware of the logistical difficulties this plan posed, they collected together all America’s top mountaineers, paid them handsomely and gave them a table-sized nuclear powered listening device. After a season’s training on Alaska’s Mount McKinley, America’s newest and most improbably spying unit set off for the Himalaya. Unsurprisingly their first efforts were rebuffed, but the following year the device was finally placed a good way up the mountain’s face. 18 months later, however, it stopped beaming back information. Some of the mountain’s most pristine slopes now send a Geiger counter wild.

The final act in this drama is a tragic one. They say every mountaineer has his or her mountain. For Mallory it was undoubtedly Everest; for Herzog it was Annapurna; for Willi Unsoeld it was Nanda Devi. Indeed, so consuming was his obsession with the mountain he named his daughter after it. Unsoeld had already astounded the world by traversing Everest – a kind of mountaineering finesse in which you ascend one route and descend another – but it was not until 10 years later that he was able to realise his greatest desire – the summit of Nanda Devi. In 1976 he led an expedition to the mountain to mark the 40th anniversary of Shipton and Tillman’s heroics. Accompanying him were his daughter Nanda Devi Unsoeld, a gifted and renowned climber in her own right and her fiancé Andy Harvard. It must have been something of pilgrimage for her visiting a mountain that had loomed so large in her imagination. It was a mountain with which she shared an unbreakable bond, one that was closer than even she could have imagined. Tragically in the final ascent she was overcome by the altitude. Above 23,000 feet your lungs can fill up so fast that you drown in your own fluids. As it was, Nanda Devi’s frozen and lifeless body proved too heavy for her father and fiancé to carry down the mountain in the rarefied air. In the end the two men agreed to place the woman they loved in a sleeping bag and push her off her namesake’s sheer East face.

Willi and Nanda Devi Unsoeld

Since that expedition the mountain has been declared off limits by the Indian government. Save for one recent scientific trip into the sanctuary itself, Nanda Devi has returned to something of its former unspoilt self. It enjoyed a brief and fateful engagement with man, some 50 years or so, but ultimately we were unable to sustain the link. The only remnants of that fitful encounter are, one imagines, the well preserved body of Nanda Devi Unsoeld somewhere on the slopes, victim of an obsession.

Officially the government’s decision to isolate the mountain once more is designed to protect the fragile and unique ecosystem inside the sanctuary. But somewhere there must be at least one other concern: to remind us that however full the world gets, unknown places remain. And that I find curiously comforting.