Episode guide

Underground Worlds

Series 1

Underground Worlds

  • Sweden

    Exploring Sweden's passion for subterranean spaces, and how the nation has taken extraordinary precautions to protect itself - by excavating an astounding 65,000 nuclear bunkers.

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  • Switzerland

    A look at some of Switzerland's 300,000 subterranean bunkers, the creation of a local entrepreneur shrouded in mystery in England and a network of tunnels deep beneath Slovenia.

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  • Bouzincourt

    A labyrinth of tunnels underneath a tiny French village which contains mysteries from several historical eras, and a Welsh slate mine that has been given a new lease of life.

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  • Kingdom of Salt

    The Wieliczka Salt mine in Poland, some 327 metres deep, where the voids left behind from excavating salt have been transformed into extraordinary spaces, carved by hand.

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  • City of Naours

    An underground city beneath a forest in Northern France built to house 3,000 people, an ice cave under Iceland's biggest glacier, and a subterranean power station in London.

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  • Gibraltar

    Incredible feats of human endeavour, revealing what people have built, where they've built it, how and why. The first edition focuses on hidden tunnels and caves in Gibraltar.

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  • Jersey War Tunnels

    The underground bases built by the German army during the occupation of Jersey, and a group of more than 20 underground cities in Turkey, one of which dates back to 800BC.

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  • 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.

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  • Edinburgh Vaults

    The sinister history of Edinburgh's vaults and the development of Helsinki's subterranean spaces. Plus, the impact of the building of Naples on the volcanic ground below.

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  • Dover War Rooms

    Exploring the military headquarters built beneath Dover Castle during the Second World War, and Odessa's catacombs, possibly the largest tunnel network in the world.

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Underground Worlds

Series 2

Underground Worlds

  • Grand Canyon's Lost Treasure

    Exploring inside the Grand Canyon Caverns - North America's largest dry cave system. Plus, Cold War radar bunkers around the UK.

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  • Murder Raid Tunnels

    Exploring the extensive air raid tunnels hidden beneath Ramsgate. Also, how the former thriving mining town of Butte, Montana repurposed the 10,000 miles of tunnels.

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  • Hotel Bunker of the Apocalypse

    Exploring the secret, Cold War US government bunker hidden under Greenbrier Hotel, West Virginia; Plus, delve into the depths of a former slate mine in Wales, UK.

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  • Cincinnati's Secret Caverns

    Exploring the forgotten underworld hiding beneath the streets of Cincinati, USA. Plus, a state-of-the-art Cold War fortress on the shores of Denmark.

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  • Mystery of the Kentucky Cave

    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.

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  • Buried Lab of the Black Hills

    New. Exploring a former gold mine turned scientific laboratory in South Dakota. Plus, limestone tunnels in London and a former water cistern in Denmark.

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  • Subterranean Silo Survival

    New. Exploring old tunnels in an abandoned tin mine beneath the moors of Cornwall. Plus, former Atlas missile siloes in Kansas and tunnels hiding under Valetta.

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  • Italy's Subterranean Secret

    New. Exploring caves beneath Orvieto in Italy, originally built by the Etruscans long before the Roman Empire. Plus, a former limestone mine under Kansas City.

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  • Ireland's Underground Alcatraz

    Exploring hidden defences that have kept Cork Harbour, in Ireland, safe for over 400 years. Plus, a former submarine base in the fjords of northern Norway.

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  • Medieval Maze of Secrets

    Exploring 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.

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