S1 E8 ∙ The Maginot Line ∙

The secrets of the largest subterranean fortress along France's border with Germany, and a look at how a unique precious mineral was discovered in Derbyshire.

Series Selector for Underground Worlds

All episodes for series 1 of Underground Worlds

S1 E1 · Gibraltar

Incredible feats of human endeavour, revealing what people have built, where, how and why.

S1 E3 · Switzerland

A look at some of Switzerland's 300,000 subterranean bunkers built across history.