Himeji-jo (Himeji Castle), also called Shirasagi-jo (White Heron Castle) because of its white plastered walls, is a wooden structure built in the early 17th century under the Tokugawa Ieyasu shogunate. It consists of a main tower located on the highest point of a hill, three smaller watchtowers, several other buildings used as residences and storehouses as well as inner and outer walls. The Castle has many developed features and devices for its defense, including corridors connecting the four towers for easier mobility within the castle.