2000 feet underneath Lake Erie (because evil loves its puns), the Ohio mine stretches out for three miles. The only way to get to this portal to a salty hell is with a four-minute elevator ride, a series of airlocks and sudden primal fears of Stygian abodes. Fresh air has to be pumped down to the miners, who are also required to carry an hour's worth of emergency oxygen. Not that that's going to do them much good when they dig too deep and awaken a giant hungry dragon.

Ricky Rhodes/Morton Salt

That all feels like a lot of hassle for salt. Even their equipment makes it look like they're burrowing through an ancient alien installation in search of advanced technology, rather than in search of french fry seasoning.

Ricky Rhodes/Morton Salt

The mine produces five million tons of rock salt a year. Despite that output, the mine is sparsely populated with many tunnels left unexplored. Which leads us to assume that at least one person has wandered too far into the abyss and re-emerged months later more salt than man, babbling nonsense about the sodium gods of the ancient times.

Ricky Rhodes/Morton Salt

Okay, in reality, it's probably innocent enough, but if someday the government reveals a salt-powered superweapon capable of destroying the entire planet, maybe postpone that Great Lakes fishing trip for now.

Designed to enable the government to keep sending orders topside for up to three months, Burlington is over a kilometer (0.62 freedoms) long and featured fun amenities like a bakery, darkroom, library and a "VIP Room" (how s****y would it feel to be one of few people chosen to ride out a nuclear apocalypse, but still not be allowed in the VIP section?). Purportedly, it also had a pub called the Rose and Crown, because the Atom and Mutant would have been too on the nose. The whole project was so secretive that not even most of the people picked to live in it knew about it, which does explain the VIP room.

Ministry of Defence

The British government has stopped funding Burlington, and it's falling into disrepair. So if you're looking to unleash an evil scheme upon the world and don't mind working with technology that hasn't been updated since the '80s, there would be an undeniable dramatic irony in buying up Britain's own government fallout shelter to wage supervillainy against them. The government even put it up for sale in 2005, then quickly pulled it off the market. Probably because they only got one offer from a certain E.S. Blofeld looking to trade his mountain home in for a place with an easier commute.

Ministry of Defence

Here's a man standing in one, to give you a sense of weird yet adorable scale.

Richard Pope

The whole thing is like a Pixar movie about the secret world of tiny trains, and those tiny trains subsequently being devoured by the monsters from a Guillermo del Toro film.

They'd make a great setting for the next Bond movie. Imagine the thrilling underground chase from Skyfall, except that Bond is hunched over and constantly bonking his head. Or how about the next Fallout or Metro game being set in a grim post-apocalyptic London where only little people survived? Alternatively, London is planning to open certain sections of the tunnels to tours later this year, so if none of your ideas strike your fancy, you could always go check them out yourself, then sneak away into the shadows to become yet another postmoleman still roaming the tunnels.

Matt Brown, Matt Brown

Government workers use them to move files between buildings and some even jog in them when they need to exercise and both the gym and the outdoors are just too pleasant and inviting. Also, movies have been filmed there; they were used for air raid drills; the homeless have been temporarily sheltered in them; and, back in the '50s and '60s, they were used to shuffle infamous criminals from holding cells to the courthouse. In 1960, when property taxes were still paid with cash, the government carefully moved a billion dollars through the tunnels in the middle of the night, in a top secret operation that took three months to plan.

In less verified stories, the tunnels were supposedly also used to run hooch during prohibition, Charles Manson's followers were said to have plotted to bust him out of jail by using them, and in one abandoned tunnel, all the beautiful actors and actresses come together once a month to make fun of your Facebook pictures.

Alyssa Walker

But before you start considering buying your own little plot of underground bunker in case society ever needs a hard reset, SubTropolis is strictly for business. The cave system is home to about 10% of Kansas City's commercial interests and the reason for moving their business into this underground wonderland might be the most boring one ever: to save on heating bills. Being underground keeps energy costs way down thanks to the consistent temperature, and it's great for storing sensitive material, because it's a gigantic underground maze.

Connie Zhou/Bloomberg Business

Above you see a USPS stamp distribution hub, shelving space for the National Archives, and a library of old films that includes the original print of Gone With the Wind. But there's also a science center for kids ...

Connie Zhou/Bloomberg Business

... and c'mon, the whole thing is obviously just a front for a Hank Scorpio-esque feat of villainy. Their official introductory video even calls it a "business labyrinth," so there's clearly a secret Flamethrower District that cameras aren't allowed to see.

That's Old Sacramento, which, no, isn't buried under what is now East St. Louis, but actually the modern and vibrant city of Sacramento! Back in 1861-62, Old Sacramento was devastated by floods that killed thousands and left the streets underwater for three months. So, over the course of 15 years, two and a half miles of the city were raised by nine feet, because sometimes keeping mad scientists on the municipal payroll really pays off. Parts of Old Sacramento have been lovingly preserved, a permanent testament to America's history and a bygone way of life. Other parts of Old Sacramento look like you'll get de-boned by a f*****g vampire if you're caught there past sundown.

Rebecca Crowther/Center for Sacramento History

Sacramento isn't the only city to find new life on top of its own corpse. The Great Seattle Fire of 1889 forced the city to rebuild 31 blocks, and while they were exploring bold ideas like "fireproof building materials," they also decided to elevate the city above the swampy tidelands the original streets had been built on. But by the time they started regrading the streets, some buildings had already been rebuilt, sort of like when your landlord didn't tell you that you were evicted until after you finished retiling your bathroom. That resulted in the Seattle Underground, a city below the city, once home to the urban blight of opium dens and gambling parlors, now home to the urban blight of tourists and the walking tours that prey on them.

Razvan Orendovici, via Wiki Commons

Legend has it that, to this day, flannel-clad ghosts haunt the halls, understandably pissed that they rebuilt their banks and bars only to have their new windows open up into scenic concrete.

Indianapolis also has subterranean catacombs, where they presumably bury whoever finishes last in the Indy 500. In the late 1880s, The city built 20,000 square feet of corridors beneath its popular City Market as a structural foundation for Tomlinson Hall, a convention centre of sorts. Those corridors proved solid as a rock, supporting Tomlinson Hall right up until the moment it burned down in 1958.

The catacombs initially helped keep meat and produce fresh before it was brought up to be sold in the morning (don't forget to tell your fridge how much you appreciate it), then served as a homeless shelter in the brutal 1912-13 winter. They were used as a police firing range in the 1970s, hosted a Super Bowl party in 2012, and have no doubt been the site of countless teenagers getting a haunting first handjob, among other historic events.

Greg Wagoner

Also, according to local legend, it's f*****g loaded with ghosts, but that's probably safe to assume about everything we've just shown you.

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