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10 Episodes 2021 - 2021
Episode 1
Thu, Aug 5, 202145 mins
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.
Episode 2
Thu, Aug 12, 202145 mins
Exploring the vast 400-mile Mammoth Cave in Kentucky, USA. Plus, a newly constructed opening into a metal mine in Wales - untouched for over 70 years.
Episode 3
Thu, Aug 19, 202145 mins
Mysterious caverns in the city of Cincinnati are examined. A network of cellars, wells and tunnels in Cincinnati that were used to create the world's most popular beer. Plus, a state-of-the-art Cold War fortress on the shores of Denmark.
Episode 4
Thu, Aug 26, 202160 mins
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.
Episode 5
Thu, Sep 2, 202145 mins
Exploring hidden defences that have kept Cork Harbour, in Ireland, safe for over 400 years. How did this powerful stronghold became a brutal and terrifying prison. Plus, a former submarine base in the fjords of northern Norway.
Episode 6
Thu, Sep 9, 202160 mins
A decommissioned missile launch facility in Kansas remained one of the best kept subterranean military secrets of the Cold War, and now, experts reveal how this abandoned underground complex transformed into a state-of-the-art survival bunker.
Episode 7
Thu, Sep 16, 202160 mins
Exploring caves beneath Orvieto in Italy, originally built by the Etruscans long before the Roman Empire.
Episode 8
Thu, Sep 23, 202145 mins
Exploring inside the Grand Canyon Caverns - North America's largest dry cave system. Plus, Cold War radar bunkers around the UK.
Episode 9
Thu, Sep 30, 202145 mins
Exploring the extensive air raid tunnels hidden beneath Ramsgate.
Episode 10
Thu, Oct 7, 202145 mins
Exploring the maze of of long narrow tunnels beneath Exeter that were built in medieval times to protect the city. Plus, a marble quarry under the pine forests of Vermont.