There is a glitch towards the top of the empire state building right below the edge of the last ledge yout don't need cheats you can do this in multi. and is very easy. all you do is fly a heli into the area and you will simply fly through the building and you can stop inside and then drop under the city and fly under the city with. very fun to do in multi because people don't know where your at.

I don't know how to make a vid so if any of you do and want to make one i will gladly show you and help you do it add me on psn-cadillac256 (same as sig)
thanks
click on it and it will enlarge this is where you enter on the game.

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