Built in the 1930s under the direction of Robert Moses, the Freedom Tunnel runs from 125th to 72nd Street under Riverside Park. Until 1991 it was used as a homeless encampment, but after Amtrak resumed service through the tunnel it was completely cleared-- fifteen years later, the detritus of human habitation still haunts the place, but no one lives there. The walls of the tunnel are famous among graffiti-cognoscenti-- skylight grates every twenty or thirty feet create sun-lit exhibition spots. Deep inside the tunnel you can find some classic pieces by Freedom (whose nom de guerre gives the tunnel its name), Twist, Revs, Cost, and Sane/Smith-- and more recent stuff from Kuma and Deuce Seven.