Facebook is building a server farm in northern Sweden, on the edge of the Arctic circle. The average temperatures there are so cold that they won't need to use anything but the outside air to cool 600,000 square feet of servers. But even so, the server farm will use as much power as 16,000 homes. In effect, Facebook is building its own little city for its servers.

Fortunately, Facebook has picked its site well: The server farm will be close to a hydropower plant that produces twice as much electricity as the Hoover Dam. The dam on the nearby Luleå river regularly makes more than enough electricity for the region, so they have some to spare. So the power-hog servers can be run on renewable energy.