It looks innocent enough: a cute little cabin just outside the Kristallhütte, in the Hochzillertal ski area of Austria. It’s just by the place where you stop and click out of the skis, before piling into the warm interior of the main bar and restaurant.

But if you fancy adjusting your hair, or checking for signs of sunburn, think twice before you make use of the cabin’s one-way mirror windows. Because right on the other side is Kristallhütte’s very own mountain sauna.

And you know what the Austrians are like about saunas. They don’t muck about with towels or swimming trunks.

But just imagine being on the inside. How cool! In a rather hot and sweaty way, of course. The instant I saw it, I wanted to get inside and give it a go. Not only because of the utter weirdness of sitting naked at 90C while outside, at -10C, my fellow skiers and boarders were kicking the snow off their boots: but also because the interior is one of the nicest I’ve seen in a sauna. There’s a black-slate shower and a hip little relaxation room (which looks across the Zillertal, away from all the skier action). Outside the sauna itself, the wood panelling has been sand-blasted so that it has that wonderful ribbed, knotty texture you find in upmarket chalets these days. No expense has been spared.
 

 
Sadly, it’s not available to ski-in customers like me: you have to stay a night at the Kristallhütte to get the use of it – either in one of its capacious double rooms on the top floor, or in one of the igloo rooms next door. If you do, you’ll be joining an august list of former guests, which includes former German President Horst Köhler, and the current Austrian President Heinz Fischer. Which makes you wonder if they had a sauna while they were staying there…

Make no mistake, this is a remarkable place – undoubtedly one of the best mountain huts in the Alps. The sauna, the igloos, the presidential guests, are only the start of it too. Inside the main ‘hut’ there’s also a big, open fireplace, served by a circular copper chimney, and a very good, reasonably-priced mountain restaurant. On the south-facing sundeck steamer chairs are draped with sheepskin rugs, and big-name DJs play mellow sets later in the season. (When the sun shines, the temperature can rocket. The mercury once read +44C here, on an April afternoon.) Better still, it’s open to all. There’s no snotty VIP policy. Provided you buy something, you can be part of the scene.

The hut is the brainchild of Stefan Eder, and it’s been open since the 2004-5 season. And get this: he opened it when he was 25. Stefan doesn’t own the building – he leases it from the owner. But the concept is all his. “For years, I dreamt of doing something like this,” he tells me over lunch. “And I had a very clear vision of what was needed. So when I was 22 I wrote a business plan.” It took him a couple of years to convince the owner he was right, and since then he hasn’t looked back.

He hasn’t had time. “I work 16 hours a day, seven days a week during the ski season,” says Stefan – and it’s easy to see why. He’s at that age when he wants the Kristallhütte to be cool, rather than something that makes him rich, and he pours body and soul into achieving that end.

It even goes as far as the hot chocolate. I tell him about the nastiest hot chocolate I ever drank on a mountain, in Val d’Isère, and he comments, “it was probably made with water. Most huts and restaurants do it that way, because it’s quicker and cheaper. We make it with milk.” I try one. It costs 3.50 euros, is topped with cream, and I drink it sitting in front of the fire on a sheepskin rug. It’s one of the best mountain hot chocolates I’ve ever tasted.

Click on this link for the Hochzillertal piste map. The Kristallhütte is on the left as you look at the map, near the summit of the Ofelerjoch.