Google has produced this
pretty cool interactive site that documents the travel of your email through a Google data center. They do focus pretty heavily on their own data centers. In fact, if you're actually wondering how emails are actually routed through the global network then you'll probably be disappointed. It's a good overview of the technology and work that goes into building and operating a high-end data center.
One innovation that I found particularly interesting was putting the UPS on the server board. I've seen large back-up power supplies for buildings before - one at a college and another at in Brooklyn - usually it's a huge room, sometimes more than one room, full of the
enormous batteries. Sometimes they've got back-up diesel generators too, which are also huge. Seeing all of that compressed to provide power for a data center is pretty cool. I imagine they must still have back-up batteries on site for the security systems though.