MIT: Tunnel map. It’s much more fun wandering around lost by dead reckoning and occasional, maddeningly imprecise signs. Sigh.
For the uninitiated, MIT, like many schools, has a network of tunnels beneath the buildings. Unlike many, access is not restricted and it’s perfectly reasonable to (say) hop into the tunnels from the loading docks at E25 and pop up only when you get to Lobby 7.
Of course there are less…um, pedestrian uses for the tunnels too. See this archive at Undercity.org for some starters…