Theres an huge collection of Wikipedia’s data center photos taken by Vitor Grigas, taken in 2012.

https://commons.wikimedia.org/wiki/Category:Wikimedia_servers_in_2012

Servers are located at Equinix.

Equinix hosts most of the infrastructure for Digg and Salesforce.com, and provides colocation and interconnection services to a lengthy list of marquee customers, including Google, Yahoo, IBM, America Online, Akamai, Electronic Arts, GE and Merrill Lynch.
Source: http://www.datacenterknowledge.com/archives/2009/06/09/the-internets-busiest-intersection/