The “inner moat” of Himeji Castle surrounded the castle's main citadel, with the castle tower at its center, and served as a physical barrier to prevent the invasion of outside enemies. The presence of these moats allowed attackers to take a great deal of time to reach the castle, giving the defenders time to deal with the situation. The moat was cleverly designed to create a confusing structure for the enemy to cross the channel. In addition, the shape of the inner moat and the flow of the water were designed to skillfully utilize the natural terrain while incorporating artificial elements, resulting in a defensive line that was extremely difficult for attackers to exploit.