There are a number of advantages to keeping things underground. The temperature remains near constant; energy costs are lowered; and—in the massive, 55,000,000-square-foot space known as Subtropolis—there is a whole city of workers who can keep your goods safe.

Subtropolis stores everything from a USPS collection of millions of postal stamps and the original film reels of Gone With the Wind, to a series of artificially lighted, manmade habitats used by Earth Works to demonstrate science to students.

Mining in SubTropolis began in the 1940s, and the empty space grew under the limestone bluffs on the Missouri River. By 1960, the owners realized that they had an enormous area they could rent out for business operations. The dubbed their underground city "SubTropolis" and called it "the World's Largest Underground Business Complex," a phrase that Hunt Midwest has trademarked. SubTropolis sports nearly seven miles of illuminated paved roads, and semi-trucks drive throughout the underground.

“We load and unload our trucks in perfect weather conditions,” said Joe Paris, co-founder and principal of Paris Brothers a national specialty foods company headquartered in SubTropolis. “It’s truly a green environment. We’re probably using about 75 percent less electricity underground than we would in an above-ground facility. Whether it’s electronics or whether it’s food, you don’t have temperature and humidity fluctuations and so you don’t have any condensation, moisture building up in anything. From that standpoint, in my opinion you can’t beat it.”