Under Pad 39A and 39B at Kennedy Space Center NASA built a complex of tunnels and bunkers for in case the Saturn V rocket that would bring Apollo astronauts to the moon exploded. Obviously the rooms were never used. They are rarely seen. This is an awesome gallery of photos taken from inside the rubber room.
The folks at Gizmodo point out that Google Maps has an awesome feature now that lets you tour NASA’s Kennedy Space Center. You can point and click your way through all the different parts you’d never have the security clearance to go yourself.
Needless to say I spent a nice little chunk of the evening browsing around.