Facebook is building Europe's largest server farm near the Arctic Circle in Sweden, because the severe cold will keep the servers cool naturally - lowering the energy required to crunch data from its 800 million users.

The Lulea Data Center, in Lulea Sweden, will be just 60 miles south of the Arctic Circle. Power for the mammoth 120 megawatt server farm will be supplied by nearby hydropower plants that produce twice the electricity as the Hoover Dam!

The backup alone - required to keep the servers running in the case of a blackout - is 40 MW. There will be 14 diesel generators for each of the three 300,000-square foot buildings. The project is scheduled for completion by 2014.

This is Facebook's first server farm outside the US, where it stores data in California, Oregon, Virginia and soon, North Carolina. The majority of Facebook users reside in other countries, however, so locating elsewhere will boost performance.

Facebook's Oregon and North Carolina data centers run on coal, the dominant fuel used by utilities there.

Google has a data center in southern Finland, which uses seawater from the Baltic Sea for its cooling system.