Trying to land up there is hard enough, going fishing for a quad on top of that building, takes some mad flying skills. Watch as these guys use a quadcopter to retrieve another stuck quad copter off the top of a tall building. Using basically a fishhook dangling off another quad, A simple but in this case effective (somewhat) means of getting that quad copter down from the top of that old building.
Quadcopter Rescue Mission!
Cool, stuff! Brings back fond memories when trying to rescue stuck kites in trees when I was a kid!