A "hon-maru" is a "kuruwa" located in the heart of a Japanese castle, which is a complex of "kuruwas". Fukuoka Castle was built in the style of Teikaku-shiki or Hashigokaku-shiki (a plan in which the "hon-maru, ni-no-maru", and "san-no-maru" share common defensive lines on one side, because the topography and the castle plan gives a particular advantage to that side) and its "hon-maru" is situated in the south of the inner castle. The "hon-maru" measures 125 metres (410 ft) from east to west, and 230 metres (755 ft) from north to south.