Ahh tunnels. I did the exact same thing at Duke University. There is an amazing network of industrial tunnels that stretch from West to Central Campus. Supposedly there was a tunnel that connected West to East campus, but we were never able to find it. We were able to go up random doors and end up in classrooms, the library, and even some of the on campus restaurants after everything was locked! What I do remember is how innocuous and freakin hard to find the entrances were to the tunnels! Some really low windows allowed you to slip into rooms underneath buildings, which then connected to parts of the tunnel networks. Others were just random doors that you would have NEVER have noticed before, that led straight into the network. It was crazy, and I highly recommend every Blue Devil to check it out. ;)