Season 2

2021 · 10 episodes

Episodes

1Hotel Bunker of the ApocalypseThe top-secret construction of a massive nuclear bunker remained concealed under a palatial West Virginia hotel for decades, and now, experts reveal how this vast subterranean structure was one of the most closely guarded Cold War secrets in US history.
2Mystery of the Kentucky CaveThe longest known cave system in the world spans hundreds of miles beneath the hills of Kentucky, and containing prehistoric artifacts and ancient human remains, experts reveal a subterranean mystery that may have changed the course of U.S. history.
3Cincinnati's Secret CavernsDeep beneath the streets of Cincinnati lies a network of deserted tunnels and caverns that contain a remarkable history of the city's origins, and now, experts investigate to reveal who built this underground labyrinth and why it was abandoned.
4Buried Lab of the Black HillsBuried nearly a mile beneath the Black Hills of South Dakota is a cutting-edge laboratory at the forefront of astonishing scientific research; experts reveal advancements engineers achieved more than a century ago that keep it operating today.
5Ireland's Underground AlcatrazSubterranean military fortresses situated on the southern coast of Ireland have protected against enemy invasion for over 400 years, and now, experts investigate how this powerful stronghold transformed into a brutal and terrifying prison.
6Subterranean Silo SurvivalExperts investigate a decommissioned underground missile launch facility.
7Italy's Subterranean SecretAn unprecedented landslide unveils a hidden world beneath a picturesque town in northern Italy, and now experts investigate this vast network of tunnels and passageways that stretch 300 feet underground to reveal the city's subterranean past.
8Grand Canyon's Lost TreasureDescending more than 200 feet beneath the Arizona bedrock lies the largest dry cave system in North America; experts explore this vast subterranean network to reveal the mysteries and undiscovered treasure that remain hidden within its walls.
9Murder Raid TunnelsExperts explore an extensive network of tunnels beneath Ramsgate, England.
10Medieval Maze of SecretsA forgotten world of ancient underground passages and medieval engineering lies hidden beneath the town of Exeter, England; experts investigate and reveal how this ambitious tunnel system was the result of one of the deadliest epidemics in history.