An outer castle is a "kuruwa" that includes the castle town, comprising samurai quarters, commoners' dwellings and temples. This "kuruwa" is clearly demarcated by defensive lines which consisted of moats, mound lines and gates that separated it from the areas outside the castle. Various writers of old texts differ with regard to the exterior boundaries of the outer castle of Fukuoka Castle; some indicate a smaller area, and some indicate a larger area, but when considering the viewpoint of the science of fortifications, it can be said that the Naka River, the Hizen Moat (present-day Tenjin 1-2 chome), the Naka Moat (present-day Daimyo 1-2 chome), the inner castle, the Tojin-machi-guchi Moat (present-day, Kuromon-gawa-dori Street), and the sea define the boundaries of the outer castle of Fukuoka Castle. The outer castle of Fukuoka Castle measures no less than about from east to west.