There is more to Kansas City, Missouri than what you see on the surface. In fact, 10% of its industrial real estate is underground. Situated atop vast limestone deposits, Kansas City was a prime location for underground development. One notable example is SubTropolis, the world’s largest underground business development. Dug into the Bethany Falls limestone mine, on the bluffs of the Missouri River, SubTropolis is, in places, 160 feet (49 m) beneath the surface.

SubTropolis was created through the mining of a 270-million-year-old limestone deposit. In the mining process, limestone is removed by the room and pillar method, leaving 25-foot square pillars that are on 65-foot centers and 40 feet apart. The limestone strength is six times that of concrete, measuring in at 18,000-24,000 pounds per square inch.

Its tunnels are 16 ft (4.9 m) high and 40 ft (12 m) wide. Through ongoing mining, about 3.2 acres (13,000 m²) of available space are added each year.

Mining in SubTropolis began in the 1940’s. By 1960, the owners realized that they had an enormous area they could rent out for business operations.

More than 1,700 people spend their workdays in SubTropolis, which serves primarily as a secured storage facility that houses such varied things as a US Postal Service collection of millions of postal stamps, the original film reels of Gone With the Wind, and a series of artificially lighted, manmade habitats used by Earth Works to demonstrate science to students.

The details are impressive:

• State-of-the-art fire sprinkler systems monitored by a centralized computer
• Commissioned security officers on-site 24-hours-a-day, 7-days-a-week
• Professional on-site management
• Full-time maintenance crew
• Over 6,000,000 square feet of leasable space
• More than 8,000,000 square feet for expansion
• 8.2 miles of lighted, wide, paved roads
• 2.1 miles of railroad track
• More than 500 truck dock locations
• Served by over 300 truck lines
• More than 550 international, national, regional and local companies
• More than 1,700 employees
• More than 1,600 parking spaces
• Over 10,000 limestone pillars
• Over 55-million square feet

Employees spend their days in consistent temperature and easily controlled humidity levels, never having to worry about rain, snow, or even tornadoes.

SubTropolis is just one — but the largest — example of such underground centers of Kansas City. Other such subterranean complexes in the area house the records of the Internal Revenue Service and the National Archives, just to name a couple.