Microsoft's new $500 million Chicago data center is one of the largest data centers ever built, spanning more than 700,000 square feet. But it's also one of the most unusual, with its garage-like lower level optimized for 40-foot shipping containers packed with web servers, while a second story houses traditional raised-floor data center space. About a dozen parking spaces in the "container canyon" are occupied by containers packed with servers and, in some cases, equipment to power and cool the servers. Each row of containers plugs into a spine providing hookups on the lower level, with power distribution equipment on a mezzanine level. With double-stacked containers, portable stairs can be wheeled in to provide access for maintenance.