A large castle was divided into an inner castle that surrounded a palace where the governor lived and an outer castle that surrounded the entire city, and the inner castle was called a castle and the outer castle was called an enclosure, and the whole structure was called a citadel.
大規模なものは、宮殿など支配者の住む場所を囲む内城と、都市全域を囲む外城に分かれており、内城は城、外城は郭と呼ばれ、併せて城郭といわれる。