The forbidden city is to represent the supreme power of the emperor given from god, and the place where he lived being the center of the world, all the gates, palace and other structures of the forbidden city were arranged about the north-south central axis of old beijing. for security the forbidden city is enclosed by a 10-meter-high defensive wall. Which has a circumference of 3.430 meters. at each comer of the forbidden city. there stands a magnificent watchtower , which was heavily guarded in the past around the city there is a moat as the first line of defense