Amazing Cities Hidden Right Beneath Your Feet

You're probably familiar with the most famous part of Paris's underground city, and that's because it's equal parts creepy and awesome. The catacombs are the final resting place for between six and seven million people, and to put that in perspective, that's the human being equivalent of, roughly, Rio de Janeiro. The tunnels already existed when they started burying people there, and they date back to around the 13th century. Limestone was quarried from beneath the city to build on top of the ground, and while that doesn't really seem like the best idea, we're not here to judge. In the 18th century, the body count rose, cemeteries overflowed quite literally, and the city started smelling so bad that even the perfume shops started complaining. The bodies were moved underground.

About a mile of the catacombs are open to the public, but there's another part of the underground of the City of Lights—we like to call it the Underdark—that's definitely not as public.

Around 185 miles of tunnels are under Paris, and while you're not technically supposed to be there, people have never let technicalities stop them. In 2004, law enforcement found that someone had set up an underground movie theater in part of the tunnels near the Eiffel Tower, along with a lounge, workshop, dining area, and bar. It's all the work of a group called The Mexican Consolidated Drilling Authority, give or take some translation difficulties. According to their spokesperson, Lazar Kunstmann, they're just one branch of an organization dedicated to mapping and preserving the tunnels ... and having a bit of fun. At the time the movie theater was found, Kunstmann went on record saying seven other sites are also deep in the tunnels under Paris, but that's all he'd say. Secret tunnels, a secret society, and code names. It couldn't get any better.

Those in the Western world weren't the only ones who spent years worried about the very real possibility of nuclear war, and in 1969, China's Chairman Mao ordered a nuclear blast-proof city excavated from underneath Beijing. It's still there, and no one's sure how much of it was completed before the project fell to the wayside. It's more than just a series of tunnels. It includes actual underground recreations of some of Beijing's most famous areas, like Tiananmen Square.

A lot of the tunnels are flooded and filled, with every kind of mud, muck, and worse that you can possibly imagine, and as unthinkable as it might be, it was briefly opened as a tourist attraction because, why not? Go into another section of the tunnels, and they're called home by a group of as many as a million people unkindly called the "rat tribe" by the Chinese media. Unable to afford—or find—above-ground housing, this particular demographic (usually young, usually newcomers to the city, and usually holding down more than one job in hopes of moving up, quite literally), they live in the tunnels, bomb shelters, and basements that make up an entire underground city. Those who do make it above ground are considered success stories, and that's some dark stuff.

Some archaeologists spend their whole lives looking for that one discovery that's going to put their names in the history books, and sometimes, they're walking on it without knowing that it's even there.

For years, we knew some sort of little, unimportant settlement was on a hill called Strongilovouni, but it was sort of the North Dakota of Greece. Sure, people lived there, but they were ordinary people, and no one gets global recognition for saying, "Hey, ordinary people lived here in a few huts!"

Fortunately, researchers from the University of Gothenburg and the Swedish Institute at Athens were curious as to just what might be there, and they dug out the ground-penetrating radar and went looking. Not only did they find things like walls and towers, they found a sprawling, actual city that's almost 100 acres—and that's just inside the city walls—hidden in the hill. They think it was a pretty important place that thrived for a couple hundred years, starting around 500 BC.

Almost overnight, that area of Thessaly went from backwoods, east-of-nowhere to home to a decently large city that we know nothing about. Take note, history. Sometimes, the little guys are important after all.

Not long ago, the possibility of all-out nuclear war was a thing, and that's why the British government built a sprawling, 35-acre complex under Wiltshire. Started in the 1950s and designed to completely support up to 4,000 people for at least three months with no need to access the outside, it was Britain's contingency plan for if there was ever a need to go from Code Red to Code Brown Trousers.

There were hospitals and cafeterias, laundries, generators, and even an underground lake and water treatment plant. It had a code name, too—Burlington—and some of its 60 miles of roads were even named after roads in the world's major cities.

The public has known about Burlington since it was decommissioned in 2007. At the time, a certain part of the population was convinced the underground city was home to aliens and UFOs. (To be fair, people probably still think that.) It was rumored to be the UK's version of America's Area 51, and while the truth is different, it's no less cool. Burlington was kept secret for decades, so secret that desks and offices were assigned to civilian personnel who had no idea the compound existed. Think about that. You could have your own desk in a top secret military facility right now, and you might not even know.

Sometimes, it just takes something catastrophic. In 1889, a massive fire devastated Seattle, and that was almost all right. Even at that time, the city had been plagued with drainage problems and flooding, because let's face it, few cities have ever been built with an eye toward these sorts of things. When it was decided that the city would be rebuilt, they figured they might as well do it right, build on a higher level, and try to avoid the previous Seattle's problems.

Since some people just aren't patient, by the time this was decided, landowners had already started building right in the same spot. When someone knocked on their doors and pointed out the obvious, something of a ground level was already built. It was decided that this would be left, and the new "ground level" would be built on top of it. By 1890, crossing the street might mean needing to climb 35 feet up a ladder, but things got sorted out.

Not long after the city was rebuilt, the lower levels were condemned for the disease pits they were ... but that's never been enough to keep people honest. At the time Seattle was being rebuilt, the strange dropped sidewalks and tunnels left all sorts of secret places for a certain type of occupation: "seamstresses." These seamstresses didn't sew, and taxes on their "entertainment" activities accounted for about 90 percent of the city's revenue over a period of nine years. You can still visit the tunnels, but the seamstresses are gone.

Head north out of Avignon, France (you know, if you're in the neighborhood), and you'll come to a strange hill that looks out over the Rhone Valley. Inside are a series of caves that people have called home for so long that we're not even sure why they were first built there, and there's a very good reason for that: we hadn't invented writing yet.

The caves of the Barry Troglodyte Village have been legitimate homes for long enough that the best we can do is "sometime since the Neolithic era," which is generally accepted to have started around 10,000 BC. For some context, this was the time when we were just figuring out how to grow grains, use stone tools, and become such good friends with animals that they'd stay with us until we ate them. (We've never been nice people.) It's thought that the cave system with the incredible view was inhabited pretty much continuously up until the 20th century, when there was only one elderly woman and her servant left in the underground village. They only packed up and moved out because parts of the cave homes collapsed and killed off some of their neighbors, and honestly, some wear and tear is expected when you're living in a 12,000-year-old home. They don't build 'em like they used to, that's for sure.