I explored the campus thoroughly, but it was not until several years after I graduated that my eyes were fully opened to the wonders of the university's subterranean world. There are four different tunnel systems under the York University campus. The water drainage tunnels and sewage tunnels aren't very tempting to the explorer, nor do they go anywhere special. Slightly more interesting are the pedestrian tunnels, which burrow beneath a large part of the campus and connect most of the different colleges and lecture halls. These pedestrian tunnels are fairly chaotically laid out and are very nicely decorated with graffiti - unfortunately, the pedestrian tunnels are open to the public and therefore not very interesting.
Steam tunnels are poorly lit, dirty, cramped, dangerous and uncomfortably hot.
The bad news is they are strictly off-limits. Generally, school administration will manage to outlaw their use without ever admitting to their existence. Students caught in the tunnels are threatened with expulsion and non-students are threatened with serious fines. In spite of this, in colleges and universities across North America it has long been a popular student pastime to descend into the tunnel network and explore. The tunnels also conduct cold air, electrical wires, telephone lines, network connections, natural gas.