The main keep or tower (known as the ) was in the northern corner of the "Honmaru" ward. "Kitahanebashi-mon" is right next to it and was one of the main gateways to this innermost part. The measurements are in width from east to west, in length from north to south, and in height. A five-storey keep used to stand on this base which was in height and was thus the highest castle tower in the whole of Japan, symbolizing the power of the "shōgun". The keep and its multiple roofs were constructed in 1607 and ornamented with gold. It was destroyed in the 1657 Fire of Meireki and not reconstructed. The foundations of the keep are all that is left.