Season 2

Uncover the technological leaps that have enabled the world's longest tunnel, the Gotthard Base Tunnel, to come into being. Stretching 57 kilometres through the Swiss Alps, it ranks as the deepest tunnel on Earth and forges a vital high-speed rail corridor between Zurich and Milan. About 2000 workers, guided by four gigantic tunnel-boring machines, excavated 24 million tonnes of mountain rock to complete the tunnel. This program traces the six engineering breakthroughs that made the project possible, and highlights six landmark tunnels, including the Thames Tunnel and Channel Tunnel, each showcasing an ingenious innovation that has enabled tunnels to extend ever further.