SubTropolis: The Business City Hidden Under Kansas City, Missouri

Kansas City is built on limestone, literally. Beneath the city lies a layer of Bethany Falls Limestone about 20 to 24 feet thick, and for much of the 20th century, companies mined it to build the city above. Much of Kansas City, its roads and highways, and even the runways at Kansas City International Airport, were built with rock from one mine in the bluffs north of the Missouri River. The miners didn't dig down. They tunneled sideways into the hillside, using a method called room and pillar: carving out wide rooms while leaving massive square columns of limestone standing to hold up the roof. Over the decades, they hollowed out more than 55 million square feet of space, held up by more than 10,000 pillars, each about 25 feet square. What was left behind turned out to be valuable. The chambers were dry, secure, about 150 feet underground, and stayed at a steady temperature all year. They could also be entered at ground level, so trucks could drive straight in. Lamar Hunt, the founder of the Kansas City Chiefs, saw the potential. His company, Hunt Midwest, began turning the mined-out space into commercial real estate, and the first underground business space opened in 1964. Hunt called it SubTropolis and trademarked a bold slogan: the "World's Largest Underground Business Complex." Above part of the mine, on the surface, Hunt Midwest also developed the Worlds of Fun amusement park. Today SubTropolis works like an underground city. Its streets are paved, 40 feet wide, and lit by more than 10,000 LED lights, and addresses include the number of the nearest pillar. Hunt Midwest says it has more than 10 miles of paved roads, along with several miles of rail track, more than 8 million square feet of leasable space, and more than 2,000 people working underground. Semi trucks and freight trains move through the tunnels, serving warehouses, distribution centers and other businesses. Thanks in part to SubTropolis, about 10 percent of Kansas City's commercial real estate is underground.