Iron Mountain datacentre, Pennsylvania, US
Built in a limestone mine, this experimental data centre room cools equipment directly into the limestone, which can absorb 1.5 BTUs per square foot. Because of this absorption, the test room uses no cooled raised flooring, and it directs heat through ceiling panels and blows it across the roof of the shafts to cool. The facility also uses water from an underground lake to cool. The goal is to determine the site's geothermal properties and take advantage of them to save money.