Horikawa River runs on the other side of Horikawa-dori Street across from the square in front of Ote-mon Gate; even though it [the river] does not quite constitute Suguruwa [completely surrounding the castle with a moat or a wall], it might have been envisioned to provide the first line of defense.
大手門前の広場と堀川通を隔てて堀川が流れているが、総郭とまでは言えないものの第一防御線として想定されていた可能性はある。