One of Google's most fun web-based facilities is StreetView, which lets you walk down a virtual version of almost any street in the world.  You can even take a StreetView tour inside buildings, such as some of the world's best museums and art galleries.
Conversely, one of Google's most closely-guarded secrets (literally) has always been its datacentres; the buildings that hold the servers which contain all of Google's content.
But now, Google has added a virtual tour of one of its US datacentres to StreetView.  You can walk straight in through the front door, past the noticeboard and the pinball machine, up the stairs, and into the datacentre itself.  You can even walk among the racks of servers.  And all you need is a web browser.
Click onto https://maps.google.com/maps?hl=en&ll=35.898645,-81.548671&spn=0.005945,0.012306&sll=35.900197,-81.547024&layer=c&cid=7373938251588581469&panoid=QJRzrgIKmN4uPQg7lmOGww&cbp=13,119.83,,0,3.72&gl=US&t=m&z=17&cbll=35.898621,-81.548447  and see for yourself.