Top 10 Cities for Urban Exploration

Big draw: Beelitz-Heilstätten Hospital

Long before Adolf Hitler was chancellor, he was treated at Beelitz-Heilstätten, a WWI-era military hospital, for a leg wound as a young soldier in 1916 [source: Hawkins]. Almost 80 years later, deposed East German dictator Erich Honecker was treated there for cancer.

The sanatorium was built in the late 1800s to deal with Germany's tuberculosis outbreak, and the complex is accordingly massive. It later became a German military hospital, then a Russian military hospital, and ultimately the stalking ground of a serial killer named Wolfgang Schmidt [source: Chalk].

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Next, to Belgium ...

Big draw: Abandoned crypt, Laeken

Certainly Europe has no shortage of abandoned grave sites, but the town of Laeken, near Brussels, has a particularly good one (as far as these things go).

A series of tunnels runs beneath a cemetery in the village -- tunnels housing nearly 100 years of the city's dead in vault-lined walls. The crypt was abandoned decades ago when authorities determined the maintenance was too expensive, or so the story goes [source: Colette].

Crypts are eerie places. This crypt is remarkably so. Icicles hang from streaky skylights. Hazy light falls on inscribed names and dates of the dead, most still entombed there. Some vault covers are absent; dark, empty, coffin-sized spaces dot the walls. Flowers, most dead, some plastic, lie where family members left them on their last visits, lending the place a creepy sense of unexpected abandonment [source: Colette].

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Now, to the American West ...

Big draw: The airport (That's right, the airport.)

Denver International Airport (DIA) is more than simply one of the largest and busiest in the world. It's also the subject of some of the most bizarre conspiracy theories of modern times.

There are tunnels there -- extensive networks running beneath the airport -- where few people are allowed entry.

Aside from baggage handlers, that is. These tunnels were built as the main routes of a state-of-the-art baggage-handling system designed specifically for DIA, which failed immediately and miserably, and currently host the working, low-tech system that gets bags from one end of the sprawling airport to the other [source: Johnson].

Some conspiracy theorists believe the airport was built as a decoy -- a sort of key to the unfolding of the end of days or a secure location for the righteous when that time comes. Secret governments and the Freemasons play into the theories, too.

Those tunnels are essential to the story, but there's more: DIA was (somewhat controversially) constructed in what used to be the true middle of nowhere, far from the city center and general populace; inside, commissioned murals depict apparently apocalyptic messages; and an inscription in one terminal wall seems to loosely reference the New World Order, a famous conspiracy theory involving a one-world government [source: Mahers].

Access to the tunnels is restricted, of course; but most of the other evidence is open to the ticket-holding public.

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Then, eastward ...

Big draw: Packard Automotive Plant

It's no surprise that the parts of "Motor City" abandoned by the motor makers would offer a lot of ghost-town structures. The Packard plant is one of the biggest. It was built in 1903, closed and converted into an industrial complex in the 1950s, closed again in the 1990s, and finally looted down to nothing [source: Detroiturbex].

Now, what's left is the damaged bones -- brick walls, scattered cinderblocks and beams warped by fires no one puts out; frames of the between-building bridges that sheltered workers in the Detroit winter; mounds of tires, rubble and broken glass; and the occasional truck driven into the building to haul away looted materials, oddly left behind.

The structural state of the plant is such that the fire department has been ordered to stay out -- thus the fires burning freely [source: Lam].

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Heading now across the Atlantic ...

Big draw: The London Underground

It's the oldest subway system in the world, with initial construction dating back to the 1850s, offering urban explorers something most underground railways can't: a seemingly unlimited supply of unused tracks, tunnels and stations.

There are long-vacant stations, including Down Street, which closed in the early '30s; and ones like Aldwych, closed to the public in the '90s (but still open to the occasional film crew), both of which sheltered Londoners during World War II bombing raids [source: Cooper].

Other underground paths, like the well-secured Post Office Railway line that closed in 2003, were in use so recently they offer a tour of lines in near-working condition for the most resourceful of urban explorers (read: those willing and able to commit the felony of breaking in) [source: Silent UK].

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Back to the United States, the Midwest now...

Big draw: The Labyrinth

"Tunnel system" would be a ridiculous understatement. Beneath the city of St. Paul, Minn., a massive, varied, nearly pristine world of interconnected tunnels reaches at least five stories deep and goes on for miles. Built in the 1800s in the heart of the city, it includes seven very different but ultimately connected systems, some overlapping in areas, some still in use, serving such varied utilities as phone systems, sewer systems, water and gas lines and power for the city's long-gone electric street cars. Each system reveals different architectural styles, with occasional carvings in the sandstone walls, presumably the work of those building the tunnels [source: Action Squad].

No one is allowed in. Access requires rappelling skills.

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Moving northeastward ...

Big draw: The "Freedom Tunnel"

In the 1930s, Amtrak ran underground commuter trains from a hub in Manhattan. The tunnels were abandoned when cars reduced the need for that network, and now they're some of the most famous in the world.

Between 1980 and 1996, graffiti artist Chris "Freedom" Pape painted murals on the tunnel walls -- thus the unofficial name [source: Vandalog]. But the tunnel has come to mean more than that.

Depicted in the 2000 documentary "Dark Days," the Freedom Tunnel was for years home to outsiders, people no longer able to or interested in living in the world above ground. There was a whole dark city down there, right under Manhattan, now abandoned again but still displaying the art for which it was named and physical reminders of the people who lived there.

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Big draw: The Paris Catacombs

In the late 1700s, an outbreak of infectious disease was traced to a cemetery in Paris. To save the living, the dead were unearthed and moved to old quarries beneath the city [source: Catacombs Museum]. Those quarries are part of the subterranean network known as the Paris Catacombs.

Over several decades, every cemetery in Paris was emptied, the bodies relocated to the tunnels that would finally come to house about 6 million skeletons, stacked against the tunnel walls [source: Tancock].

The Catacombs are open to the public -- no breaking in required.

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Next, over in Italy...

Big draw: The Catacombs of Rome

You can't beat the Roman Catacombs for legendary significance: There are those who believe the Holy Grail is hidden in the tunnel beneath the Basilica of St. Lawrence.

The Vatican doesn't buy it, but that doesn't detract from the experience [source: cemeteries; the Christian burial tunnels date to the second century and have hardly been explored, as the Vatican owns these and seldom lets anybody enter them [source: Popes and saints are among the dead buried in the Christian crypts [source: CCofR].

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Last, to sunny California ...

Big draw: Murphy Ranch

In 1933, Hitler became chancellor, the Nazi party took over the German government, and Winona and Norman Stephens built a Nazi commune in Los Angeles.

Herr Fuhrer, they believed, would someday come to rule there. After Pearl Harbor was bombed, though, the place was emptied out, and its inhabitants were charged as Nazi sympathizers [source: Almendrala].

Now, the compound known as Murphy's Ranch, once a self-sustaining community that supplied its own power and water, stored its own food, and had its own bunkers just in case, is a vandalized shell of its former self [source: cult preparing for Germany's victory -- and, inexplicably, Hitler's reign from a ranch in L.A.

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Through almost all of this -- abandoned crypts, hospitals, forts and zoos, and orphanages -- runs the theme of neglect, and a resulting eeriness to which urban explorers seem irresistibly drawn. There's plenty of it to go around, with abandoned structures and towns and tunnel systems lying unnoticed all over the world, ripe for discovery and recording. All are accessible to those willing to risk fines, prison and death; quite a few are accessible to those who'd rather not.

Either way, the hidden world awaits.