The Underground Booty Squad
The main campus of the University of Minnesota spans both sides of the river. The east bank is much larger than the west bank, and the steam tunnel system is also much more extensive. What makes the UMN steam tunnels a class above the ordinary college tunnel system is that there are basically two systems on two different levels, one on top of the other. The shallow tunnels are about 15 feet underground, and the deep tunnels are about 80 feet underground, close to river level. The two levels are connected by numerous shafts with ladders, and a few elevators.
Most of the shallow system consists of a few tunnels radiating out from a brightly painted room in the center of the oldest part of campus, connected to the deep tunnels by one single shaft. Other segments of shallow tunnels connect other deep tunnels to a few buildings, but the deep tunnels serve as the arterial steam lines connecting the buildings on campus.
One of the unique features of the deep tunnels is the Professor's Cave - a room about 40' x 80' under a parking ramp on Washington Ave. The story goes that a civil engineering professor dug this cave for experiments, I'm not sure exactly what he was going to use it for.
There are also numerous storm drains and random sandstone tunnels that connect to the steam tunnels. All of the storm drains are locked at the river - This is the only place that I've seen storm drains with such high security!