This place is too expensive for what you get.
We stayed in the last week of the season, spent one night in the glass igloo and one night in the snow hotel.
It was clearly evident to us that the staff were ready for closing as they did not not care anymore about the guests. Everything was difficult, complicated and took forever.
In this place you need to book your food in advance and even pay for it in advance. How strange is this? The place is not child friendly as children are expected to eat the same 'sophisticated' food as adults. If you want to change the pre-selection of the food you made, they intend to charge 20euro extra. What a joke.
If you are staying in the snow hotel, the only place to be warm is in the reception building, the locker room or the room behind the lunch room. The staff just ignore you when you request a fire to be made in the room behind the lunch area even when you are cold. The staff just don't care. We waited almost 45min for a fire to be made after coming in from the cold!
The breakfast, I would rate it as super basic, maybe worth of 2 stars.
As for the sauna, you can only go once a day at a fixed time at night and at a charge. If you want go outside the set hours you pay even more.
I must say, the place is charging far too much do what it offers. The place is truly overrated and we will not come back. Rather go to the alps and stay one week in a 5star hotel. Same price but much better.