Some other structures need the construction of tunnels.
For instance, tunnels have been built on ski resorts such the ones built in Tignes, Val d'Isere or 2 Alpes in France, or Saas Fee and Zermatt in Switzerland, to allow special mass transit transport to the top of the mountain.
These tunnels are extremely steep and fluently provide safe and quick transportation to the summit of the resorts, whatever the weather conditions.
In Saas Fee, for instance, the tunnel known as “metro alpin” and opened in 1985 is the highest underground funicular in the Alps, running from Felskinn to Mittelallalin at a height of 3,500 m.