Between 1950 and 1966, thousands of men set off into the high mountains of the Valais, into a primitive landscape of rock and ice. Here, they erected a temporary civilization. From here, they blasted the rock beneath the Matterhorn and other towering peaks to dig a 160 km-long labyrinth of tunnels to bring water from 35 glaciers to the world's highest dam: Grande Dixence. Miners and intellectuals such as the writer Maurice Chappaz retraced their steps through this endless black abyss in search of the places where the overcrowded barracks once stood, of which only a few ruins remain today. This is where they surpassed themselves.

• Documentary