Beneath the bluffs on Kansas City's north side, inside old limestone mining tunnels, lies what claims to be the world's largest underground business complex. SubTropolis covers 55 million square feet of space — roughly the size of Manhattan's commercial real estate — and is home to hundreds of businesses, government agencies, and storage facilities. The USPS processes mail here, film studios store archive reels here, and a large section holds fresh mushrooms that are grown and shipped commercially.
Public access is limited — SubTropolis is a working commercial complex, not a tourist attraction — but tours are available by advance reservation. Even without a tour, the scale of the operation is visible from the entrance: trucks entering the carved limestone portals in the hillside, a full street grid underground with road signs and traffic. The constant underground temperature of around 65°F means the complex needs almost no heating or cooling — an energy efficiency story as unusual as everything else about it.