GTA IV - Glitch at hospital

Go to the hospital in NorthHolland, drive a SUV or other large car up to the red shelter at the front door. Climb onto the car, and jump from the car to the shelter. Walk to the back of the shelter and down onto the ledge on the wall where the hospital cymbal is, and then climb back up onto the red shelter, Niko will start to fall through the shelter and then jump several times before standing still.