Google has posted this really cool walk through video of a Google datacenter. But, they didn't just stop with the video. They actually took their Street View cameras through the building and used those recorded images along with true video to make the cool video seen below. It's also narrated so that you get an idea of what everything does.
It's really rather incredible the sheer number of servers hosted in the datacenter shown in the video. The place is massive and features its own networking room that is separate from the cavernous room that hosts all the servers with data on them.
Take a look at the video, and if you fancy, head on over to Google Maps and check out the self-guided tour option.