In honor of the hundreds of Columbia University freshman that have arrived on campus this week, here's the most accurate map we could find of the tunnels that run under campus. Exploring the tunnels and leaving your mark on the subterranean walls has been a popular undergraduate activity for generations-- but of course, little ones, proceed at your own risk. The tunnels are filled with boiling-hot pipes, and since the riots in 1968, the administration has blocked many passages. Before you go, it's best to read up-- the ColumbiaTunnels.org site is the best resource. If you're too lazy (or smart) to head in, check out these pictures-- they'll give you a pretty good idea of what you're missing.

Update: also check out this informative article by Michael Schreiber and Gabriel Rodríguez-Nava.

While we're on the subject of urban exploration, check out these beautiful pictures SoupFlowers took inside the Red Hook Sugar Refinery-- a building which is not long for this world.