Honmaru was surrounded with moats on three sides and the southern side faced to ninomaru across karabori (dry moat) and even troops of Nobunaga ODA could not make their way into honmaru.
本丸は三方を堀で囲まれ、南側は空堀を隔てて二の丸に面しており、さすがの織田信長軍も本丸への侵入は不可能であった。