Literally. On their own fiber network
Official Google Blog: Think big with a gig: Our experimental fiber network (http://googleblog.blogspot.com/2010/02/think-big-with-gig-our-experimental.html)

Would that be Internet 3...?:)

I remember reading that shortly after going public Google went on a buying spree gobbling up every dark fiber run they could...
http://arstechnica.com/tech-policy/news/2010/02/your-new-isp-google-launches-1gbps-fiber-to-the-home-trial.ars

Diogen.

Cool. I signed up for my community.

I wonder what locations they bought up all this dark fiber at? This could give us a hint on where we may have a chance at seeing some of this great bandwidth.