The “Ichiban Yagura” of Osaka Castle is a two-story, two-tiered corner turret located on the stone wall on the south side of Ninomaru, and was named “Ichiban Yagura” because of its eastern end. This turret serves as a flanking defense against enemy intrusion from the Tamatsukuri Exit, and has 16 windows and numerous narrow openings (openings for firing guns and arrows) on its outer east and south faces. The east side was also equipped with a stone drop to prepare for enemy attacks. Ichiban Yagura was constructed in 1628, during the final phase of the reconstruction of Osaka Castle by the Tokugawa Shogunate. It was restored three times: during the Manji period, in 1668, and in 1832. The restoration in 1832 was particularly extensive, involving dismantling. During the postwar dismantling and repairs, clothing from the period was discovered among the chestnut stones under the building. The area of the Ichiban turret is approximately 167.98 square meters on the first floor, 96.31 square meters on the second floor, and 14.3 meters high. On the south side of Ninomaru, there were turrets No. 1 through No. 7, but only the No. 1 and No. 6 turrets are still standing, and both are designated as Important Cultural Properties. The first turret survived the Boshin War and the air raids of World War II and remains intact to this day. In particular, the adjacent No. 2 turret was destroyed by fire during the Osaka Air Raid of World War II, but the No. 1 turret survived without serious damage.