On the north or south face of the tallest building fly a chopper into the left section of windows two floors down from where the building starts a smaller section (the section lit up blue at night) You must be going straight and not moving up or down. As you go in you will automatically go into first person view for a moment. As you enter, pivot right (LB) and center your chopper inside. The outer walls will be transparent. Descend with the left trigger but be sure to have the chopper just east of center as you will hit the subway and glitch out at the bottom. Go down and you will find yourself under the map. Fly around. Try to fit your chopper into buildings. Not all have floors but it's fun to play peek-a-boo with other players.