France 🇫🇷

In 2013, an unusual observation deck was built on the top of the Aiguille du Midi. Located right above the precipice, at an altitude of 3,842 m above sea level, it is completely made of glass. 

Externally, it resembles a transparent room floating in the air. The observation deck has a rather eloquent name — "Step into the void". 

This observation deck, the highest in Europe, consists of five transparent walls, floor and ceiling made of three layers of glass.