Katie Fehrenbacher for GigaOm:

Facebook’s data center here is one of the most energy efficient in the world. The social network invested $210 million for just the first phase of the data center, which GigaOM got a chance to check out during a two-hour tour. Building No. 1 is where Facebook first started designing its ultra-efficient data centers and gear, and where it wanted the first round of servers that it open sourced under the Open Compute Project to live.

Apple isn’t the only company building giant data centers. It’s interesting to see what Facebook is doing, especially since energy efficiency is a cornerstone of its design philosophy. If server farms excite you at all, the sheer scale of this is stunning.