Vanguard Packaging, a SubTropolis firm that manufactures cardboard displays for retail stores, aims for a zero carbon footprint. “We have 380,000 square feet that we’re not heating or cooling,” says CEO Mark Mathes. He hopes to install a wind turbine on the surface that would generate as much electricity as the company consumes.

Since subterranean offices lack roofs, external siding, flooring, and the usual support structures, they require fewer energy-intensive construction materials like steel and aluminum. Moreover, the low permeability of the limestone and intervening layers of shale keeps goods and records dry—an attribute, no doubt, that inspired the Postal Service to store its stamps down there.

Underground, a business’s environmental impact can be smaller, explains John Carmody, the director of the University of Minnesota Center for Sustainable Building Research, because no trees or other plants need to be cut, nor wetlands filled, to make way for commerce or industry. Gains can be made in urban planning as well, Carmody says: “By putting more resources underground, you can preserve surface land and make a denser city.”

Of course, working underground has its quirks. The weather in SubTropolis, for example, is predictable: “overcast and mid-60s,” as habitués like to say. Employees don’t get to see the sky, but what they do see, after driving through a hole in the side of a hill to reach their offices, is an endless expanse of limestone—walls, ceiling, pillars, and floor—all painted white. (Most of the “streets” are named after geologic layers of limestone and shale.) A facilities manager compared working underground to being in a mall, but the cavernous expanse more closely resembles an oversize parking garage, with some 10,000 limestone support pillars laid out in a grid, 40 feet apart. Office humor has it that, instead of getting a corner office by way of promotion, you get a pillar.

More than 10 percent of the industrial space in greater Kansas City is located “down under,” covering about 25 million square feet—an area bigger than the downtown business district. Mining limestone for use in roadway construction and agriculture continues, with additional acreage carved out each year. The same sort of facilities exist in Kentucky, Pennsylvania, and Tennessee. But with 90 percent of the world’s subsurface office space—and 45 million additional square feet available for future occupancy in SubTropolis alone—Kansas City is in the vanguard, chipping away at the energy problem one chunk of limestone at a time.