IT TAKES AROUND FIVE minutes to drive through the Great St Bernard Tunnel. Five minutes to drive three miles underneath the Alps and cross the Swiss-Italian border as you go -piazzas and pizzerias on one side, timber chalets and watch emporiums on the other. It is just about enough time for a motorist to hum along to Puccini’s Nessuri Dorma, or attempt some light yodelling. But there is an older route that runs directly over the heads of motorists in the tunnel: up above the sunroof, up above strata of met amorphic rocks and a crust of ice and snow, high among the summits where the air is thin and die passing airliners don’t seem so very far away. This route is the Great St Bernard Pass, a frozen highway counting as one of the most treacherous and storied trails in Europe.

‘Summer and winter are two different worlds up there,’ explains Eric Berclaz, leaning on his ski poles at the foot of the pass. ‘Summer isn’t a problem in winter, you need to know what you are doing.’ Eric is my guide for the ascent, and it is also his job to help decide when the Great St Bernard Pass is able to open to motorists for the summer season. ‘Summer’ in the loosest sense of the word. For just two or three months of the year, the snow melts enough for tourists to drive to the top, admire the view and maybe buy a souvenir fridge magnet from a kiosk. From September to June, the Great St Bernard Pass is plunged into a near-permanent state of Narnia: the road buried deep in snow, shivering in temperatures of down to -30°C while holidaymakers on the Mediterranean siesta on the beach not so far away. During this time, cars are of no use on the pass. The only way to cross is on skis or snowshoes.

I strap into my snowshoes for the three-hour hike to the top. It soon feels like an exercise in time travel. In the valley below, spring is arriving: wildflowers grow in the meadows and people are wearing shorts. The Great St Bernard Pass, meanwhile, is lagging a few months behind in bleak midwinter. The snowdrifts become deeper with every step. Everything is still, but for the croak of ravens and the hum of overhead power cables carrying Swiss electricity to Italian TVs and espresso machines. A few skiers and snowboarders whoosh past. Today, like much of the Alps, the Great St Bernard Pass is a place for recreation. But before the tunnel was built in the 1960s, travellers between the Italian plains and northern Europe had little choice but to come this way.

Pilgrims on the Via Francigena crossed on their way from Canterbury to Rome. Napoleon led a 40,000-strong army over the mountains, the soldiers hauling their cannons up the mountainside (the man himself sliding down on his tiny backside). Everyone from Roman legions to counterfeit cigarette smugglers traversed the Great St Bernard Pass. And there were also wayfarers who climbed into the mountain mists, and who never came back down again.  Of the many travellers on the Great St Bernard Pass over the centuries, a few people shared a rather peculiar experience. First they would have heard the rumble of fracturing snow slabs on the slopes above, then quickly found themselves spinning in a tidal wave of white powder.

Whiteness would have turned to blackness as they were buried alive. It takes about 15 minutes for someone to die of suffocation in an avalanche – during this time they would have experienced panic, coldness and a slow loss of consciousness. Standing at the gates of the afterlife, they would have seen a strange beast about the size of a Shetland pony, with giant feet and a mouth slobbering like Niagara Falls. They would then have been borne a loft by men in flowing robes, carried to a castle-like building up in the heavens. Here they would be given a cup of tea. This was no dream.

Snowflakes glide through the air as Eric and I arrive at the top of the pass. Out of the wilderness there emerges a grand doorway hung with icicles, and windows half-submerged in the drifts. We have arrived at the Hospice St Bernard, a religious hostel that has stood at the highest point of the pass since the 11th century. Its robe-clad holy men and gigantic St Bernard dogs gained fame as a mountain rescue double act: fishing passers-by out of avalanches, guiding them through fog to the safety of the hospice. Still run by the Catholic Church, the institution exists for the same purpose today: to welcome and protect passers-by.

‘This is not a monastery – and I am not a monk,’ explains Father Raphael Duchoud, a permanent resident at the hospice who today sports a dusting of fresh snow on his shoulders. ‘Monks live in silent contemplation. It is our spiritual duty to talk to visitors and welcome them: to give them food, drink and abed. Some people come here with a weight in their hearts and we try to help them. And some people arrive and simply want to know where the toilets are.’

A Swiss canon with a musical laugh, Raphael is part of a dynasty dating back to St Bernard himself – a medieval priest who had a successful sideline slaying demons, but who also built a little stone shelter for travellers in the Alps. In time, this shelter grew into a small community, with no members more famous than the giant St Bernard dogs, whose thick fur, large paws, strong limbs and sensitive smell made them ideal for res cue missions. The greatest of them all was Barry, a 19th-century super dog who made Lassie look like a slacker, rescuing as many as 40 souls and specialising in carrying hypothermic children on his back.

Today the St Bernard dogs live in an institute on the valley floor, but the two-legged community still thrives at the top of the pass. Three canons and several housekeeping volunteers supply about 50 visitors with clean beds and three generous meals a day in one of the most hostile wildernesses in Europe. The front door is open to everyone, regardless of religion. In 1,000 years it has never been locked. ‘Some people ask me why I live in the mountains, where it is winter nine months of the year,’ says Raphael. ‘But mountains are spiritual places. It is high in mountains that you can meet with the Lord.’