Atop the Washington Ave Bridge
Before they renovated the Washington Ave bridge and added the big signs on either side, it was just barely possible to climb up the emergency call boxes on either end and pull yourself up onto the roof of the covered walking level of the bridge by your fingertips.  It was a very nice place to hang out and drink.

This 1997 shot of Max Action and Muppyskum walking toward the East Bank was taken shortly before one of the other people with us jumped down on the East Bank side in front of the Weisman without checking for people, and landed pretty much right in front of a campus security monitor.

Those of us still up there thought about fleeing, but the guy didn't seem like he cared, so we just got down too.  He let us go with a warning.