this warehouse is rock-solid

Some companies, it seems, are willing to dig mighty deep in order to save energy. In June, Kraft Foods opened a 400,000-square-foot energy-efficient warehouse in—or rather, under—Springfield, Mo.

Under? Yes, indeed. Kraft's new warehouse is built into an area that was once mined for limestone. The facility's roof, ceiling, and structural columns are made of limestone, and its walls are composed of material that contains 35 percent limestone. Because the building is underground, says Kraft, it's impervious to sun, wind, and precipitation, and the vegetation that covers the building's exterior prevents storm-water runoff.

It's easier to keep the belowground building a cool 36 degrees F, so refrigeration units require less horsepower than in conventional facilities. Add in energy-efficient lighting, and the warehouse is expected to use about 65 percent less energy than a comparable aboveground building.

Springfield is home to a number of underground buildings that, like Kraft's warehouse, were developed by Springfield Underground Inc. The real estate firm leases out more than 2 million square feet of space in the limestone deposits.