Underground Marvels 2

Hotel Bunker of the Apocalypse (2021)

The 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.

Mystery of the Kentucky Cave (2021)

The 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.

Cincinnati's Secret Caverns (2021)

Deep 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.

Buried Lab of the Black Hills (2021)

Buried 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.

Ireland's Underground Alcatraz (2021)

Subterranean 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.