onezero talked about the tunnels at the university of colorado at boulder and theyre no joke. Most of the entrances to the main tunnel system are sealed off, however, there are htree ways in that i personally know of: the basement of libby, the basement of the pendulum tower ( i found this one when i was working security for a CU game and they take you down there cause theres a big meeting room off one of the tunnel branches, and it allows direct access to the third entrance), and the area under the stadium, to which theres two ways in: a door at gate 5 (the gate right next to the NROTC gate) and in the mini-gym where the indoor track is. This is a massive expanse of tunnels that goes to almost every building on campus and is fairly modern. Most of the exit doors have electronic keycard locks, but we did find that there is a tunnel that goes directly under boulder high school and a side branch that comes out in the gardens at the base of the hill below the gym (but its closed with two padlocks). However, much like the UT tunnels, the hilly landscape the campus was built on gives way for some amazing sights, and nobody ever goes down there as evident by the obscene amount of dirt on the ground in most of the tunnels and no shoeprints except our own. However, as onezero said, its a violation of campus policy to be down there and if caught, they WILL expel you. Scope it out!