London was once the world's largest city, it was the capital of the largest empire the world has ever seen, it is an ancient city, it developed the first metro system in the world, it stood at the heart of the Industrial Revolution, was the target of the London Blitz in World War 2, and feared nuclear war in the Cold War. It is not a surprise then that there is a truly massive network of forgotten and abandoned tunnels beneath the city.

Beneath this mighty city is a subterranean world of ghost Tube stations, disused shelters, and Victorian sewers. Must of what is down there remains shrouded in mystery. See here if there are secret tunnels under New York City.

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The Defense, Postal, and Government Network

Beneath London's bustling cities lies a mysterious world of Cold War-era tunnel systems and underground chambers - these number in the hundreds. Many of these are owned by the Ministry of Defense and have never been publicly acknowledged - and until recently authorities remained secretive about them. Over in Los Angeles - it too boasts its strict speakeasy tunnels.

  • Military: Many Are Secret Defense Tunnels Not Acknowledged

According to the BBC, one of the most interesting revelations in recent times is the Postmaster General's secret tunnel running right under the heart of the government at 57 Whitehall. London was at threat of a nuclear attack in the Cold War and so it was built to protect important machinery and communications. The bunker goes to the Old War Office (used by Winston Churchill during the war).

The Postmaster General's tunnel stretches to the working-class East End in a network of secret underground tunnels complete with more than 30 gears and a dozen elevators. The British government has been tight-lipped about these tunnels.

In 1950 various tunnels "disappeared" and so did a part of the budget that was used to retrofit them. In 1980 journalist Duncan Campbell managed to slip into them. Armed with a bicycle and a camera, he explored the entirety of this part of the system.

  • 1980: Tunnels Were Exposed By Duncan Campbell

He published his findings with the photos. But the government suggested they were fake and the tunnels were made in a studio. This wasn't the case as 30 years later other enterprising journalists used his access details to get in (read about it here in the Guardian).

Related: This Is How You Can See The Roman Catacombs While You're In Rome

The Scope Of The World Under London

But the secretive government, postal, and defense tunnels are only a part of London's stories. Mark Ovenden who wrote the book Underground Cities: Mapping the tunnels, transits, and networks underneath our feet stated that London "possesses one of the world’s most diverse varieties of intricate, hidden and well-used passages, ducts, and tubes beneath its streets.”

As you place your foot on a paving stone in London, you are literally walking above hundreds of miles of tunnels and passageways and ducts and sewage pipes and chambers and secret places that most people have absolutely no idea are there” - Ovenden

  • Book: Read Mark Ovenden's Book Underground Cities For An In-Depth Discussion

Some of these tunnels date back to the Industrial Revolution. Much of what is beneath the streets of London remains a mystery but there is no doubt there is a vast subterranean world off-limits. And oddly enough no one actually knows what's really down there. There's just no central place where all the data is stored. The Ministry of Defense has some information, utility companies have other information, etc.

  • Full Network: Runs For Hundreds Of Miles

There are scores of rumors that point to secret tunnels. Like that the Westminster tube station was only built after the government rejected scores of routes. These were rejected without explanation - the smoking gun is that the planned routes would run smack bang into their covert tunnels connecting government buildings.

  • Escape Tunnel: It Is Believed That Escape Tunnels Have Been Built Into Tube Lines - Like The Jubilee Line For The Royal Family To Escape Buckingham Palace

Known Abandoned Tunnels and Subways:

  • Kingsway Tramway Subway
  • The Old Vic Tunnels
  • London Post Office Railway
  • Many London Underground Stations: See The Wikipedia List

Related: The 10 Creepiest Catacombs Around The World, Ranked

Tours By London Transport Museum

For those wishing to tour this astonishing world beneath the streets of London. The London Transport Museum offers some tours of abandoned London Underground Stations. An example of one of their tours is:

Charing Cross: All Access Areas

Walk under Trafalgar Square, see disused spaces of the Charing Cross Underground station, see exclusive areas not accessible to the public. The Jubilee Line Platforms here have been closed since 1999 and have been used in filming movies like the James Bond Movie Skyfall and even Marvel’s Thor: The Dark World.

  • Price: Adult £41.50 ($56.00)
  • Duration: 75 Minutes
  • Time: 10 am, 11:45 am, 2:30 pm, 4:15 pm Each Day