It's a curious experience, being more than a mile inside a mountain and watching a coach execute a three-point turn. We had burrowed into the mountain along a road created as part of a subterranean world by the global masters of hydroelectricity, the Swiss. The mountains flanking the Haslital, and leading up to the Grimsel and Susten passes, are honeycombed with 130km of tunnels and caverns. Most take water to turbines in vast machinery halls, and it was into one of these that a metal door gave access from the road tunnel.
Wearing ear protection, we walked past spinning turbines powered by 20,000 litres of water a second, before gazing up a 774-metre shaft, which is both ventilation and emergency exit. There is no day or night here, and when the twisty road up the pass is closed by snow, the staff have to stay in dormitories until they can be relieved.
On the way back through the tunnel we stopped in front of a shutter, which lifted to reveal a sight that must be the envy of any natural history museum: a glittering crystal cave the size of a small car. The crystals started forming 16 million years ago and cover every surface of the chamber. Brilliantly lit to bring out the natural beauty of the crystals, the cave has some completely transparent crystals 20cm long. More than 40,000 visitors a year journey into the mountain by coach, car or mountain bike to see this unique place, which is just part of the infrastructure that the energy company Grimselwelt has opened up for tourism. This is partly to atone for its once rather cavalier attitude towards the environment and its responsibilities to the community; today it plays a major role in bringing visitors to the wild beauty of its watershed, organised through visitor services in Innertkirchen (00 41 33 982 26 26).
It even operates hotels that have been restored from historic buildings. Just off the road and sheltered by a belt of pines is the Handeck Children's and Family hotel (0041 33 982 36 11), where I stopped for lunch. The food is seriously good: perfectly thin wiener schnitzel is one of the restaurant's specialities, served in one of the two pine-panelled dining rooms. The menu is varied enough to keep guests happy for a week or more, and the stylishly designed rooms make it a perfect retreat for those in search of quiet in stunning surroundings with great walking on the doorstep. Children have a playground and trampoline in the garden, and mountain goats and pigs live in an enclosure. There is even a small spa and gym.
But the real excitement is 10 minutes' walk from the Handeck. I took a path following a frothing river to a 70 metre-long pedestrian suspension bridge swinging above the Handeck falls, where two rivers meet in a roaring cauldron of spray. Wresting myself from this hypnotic spectacle, I crossed the bridge to reach the Gelmerbahn funicular railway. This funicular is one of the steepest in the world, at a gradient of just under one in one (steeper than 45 degrees), and standing at the bottom of the incline gazing up the mountain it looks even steeper. It beats any fairground ride hands down. The funicular was opened in 1926 to take workers and materials up the mountain for the construction of the dam that created the Gelmersee (lake Gelmer). It opened to the public in 2001, and the single, bright red car carrying 24 passengers plus attendant, makes the 10-minute journey at a sedate two metres a second. The bench seats face downhill and passengers are restrained from falling out by a safety bar - it is that precipitous, a website for climbers describes it as "really scary"!
The funicular takes you into another world, over a shoulder of rock and out of sight of the valley floor. Little grows up here around the barren rocky shores of the lake but lichen and scrubby bushes. The lake fills a hollow surrounded by barren walls of rock majestic in scale and rising up to Alpli glacier. On a day of sun and clouds, I stood on the dam wall mesmerised as cloud enveloped the mountain, while another part of the landscape was suddenly revealed as though a veil had been lifted. A path around the lake can be walked in two hours, and there is a walk up to the Gelmerhütte for those who want a night on the bare mountain.
This year sees the refurbished Hospiz hotel reopen. This solid stone-built hotel close to the mountain's summit stands on a spur of rock at one end of the Grimselsee, and offers guests a variety of walks within easy reach, among them the Crystal Trail down to Handeck, which winds through one of the most mineral-rich areas in the Alps.
• Anthony Lambert is the author of Switzerland without a Car (Bradt Travel Guides, £14.99)
