Elbrus is the highest mountain of Russia and Europe (5642 m above sea level). It's hard to breathe on its top, you don't gasp but it's just hard to work or do anything (as if you've just run up on the tenth floor). One has to acclimatize first. There are some shelters for
acclimatization on the mountain, but around are only snow and stones. So it's better to walk somewhere near the mountain first. If you try to do it without training, mountain sickness is guaranteed: severe headache, vomiting, and in the worst case - pulmonary or brain edema.