Look for the place where you have to chase the priest into the Church missions. It is a garage-type place. Find the white stairs and climb up them. Jump over to the roof to your right, then run straight ahead. Jump off to the right of the wall. Follow this wall until you find the ramp. Once you reach the ramp, do not go up it. Keep following the wall and run to the back. Turn to the left to find the hidden location. In Grand Theft Auto 3, the sign read You are not suppose to be here. Instead, the sign has a smiley face with the message You just can't get enough of this alley, can you?.