"The only method to excavate these pieces of land safely is to freeze the soil with nitrogen. They like to call us the ice men, but in reality we put all of our heart into what we do".

Massimiliano Oppizzio, Freezing Coordinator, tells us about the magic used to transform the land into ice. They built underground passages and portals for the new M4 Metro in Milan, the deepest in Milan's public transport network.

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