Underground Marvels: Series 1
For centuries, people have built mind-blowing structures underground. This series reveals these incredible feats of human endeavor and reveals what people have built, where they’ve built it, how, and why.
Part 1: Secrets of the Rock
A hidden, subterranean city built within the Rock of Gibraltar was an immense fortress to control the seas during World War II, and new discoveries reveal the secrets of a long-lost chamber with evidence of high-stakes espionage.
Part 2: Mystery of the Lost Labyrinth
A strange, centuries-old labyrinth built into an abandoned quarry was built by an eccentric millionaire, and no one knows why; but now, a new excavation into this mysterious 9,000-foot tunnel system might finally reveal its dark secrets.
Part 3: Secrets of the Terror Tunnels
A vast system of tunnels built almost three thousand years ago was the site of the greatest battles of antiquity, and these disorienting passages could be the deadliest weapon in war; experts reveal what made this underground world so terrifying.
Part 4: The Renegades Lair
A strange underground system known as the Black Cave is connected to a fairytale castle and was home to an infamous nobleman on the run from the law; today, experts investigate the secrets he left here to discover new parts of this mysterious network.