Like many other colleges, Virginia Tech has an extensive network of steam tunnels that run beneath much of the campus. These tunnels carry steam, electricity, and telecommunications lines throughout the campus and support Tech's population of over 30,000 students and 1000 faculty. Although these people pass by the grates and manholes that lead to the tunnels every day, few realize what lies beneath.
The steam pipes in the tunnels originate at the power plant in the corner of campus and connect to most of the buildings on campus. Water at the plant is heated into steam by either coal or natural gas and then used to turn a turbine to generate electricity. The steam then travels to each building, where it is used for heating, cooking, sterilizing, autoclaving, and more.
While it's possible to directly bury steam lines, this can create problems when repairs to the steam lines need to be made and also mean that the lines cannot be upgraded as easily. While there are some direct-buried steam lines at Virginia Tech, most of the steam lines run through tunnels, which allow for easy repairs and upgrades. The tunnels also make it easy to run things like electric lines and telecommunications cables throughout the campus without digging up anything.
I'm sure it's not even necessary to mention that people have been exploring Virginia Tech's steam tunnels since they were built. This doesn't mean that you should, though. While most of the entrances are kept unlocked, many of them are in plain view. All of the tunnels have posted "No Trespassing" signs, which makes it a Class 1 misdemeanor in Virginia to enter them. It's also against university policy, although the tunnels are not specifically mentioned.
The steam tunnels are also dangerous. Since the steam pipes carry steam, they get very hot, so you can be burned quite easily. They could even burst, which would most likely kill you. If that's not enough, some sections of tunnel, particularly older sections, have asbestos insulation, which can cause all sorts of lung problems. In short, do not attempt to enter the steam tunnels.