The plan of Edo Castle was not only large but elaborate. The grounds were divided into various wards, or citadels. The "Honmaru" was in the center, with the "Ninomaru" (second compound), "Sannomaru" (third compound) extending to the east; the "Nishinomaru" (west compound) flanked by "Nishinomaru-shita" (outer section) and "Fukiage" (firebreak compound); and the "Kitanomaru" (north compound). The different wards were divided by moats and large stone walls, on which various keeps, defense houses and towers were built. To the east, beyond the "Sannomaru" was an outer moat, enclosing the "Otomachi" and "Daimyō-Kōji" districts.