Ieyasu prioritized the construction of the surrounding castletown over the expansion of the main castle enclosure by levelling Mt. Kado and reclaiming the Hibiya inlet to expand the habitable areas and build residences for vassals and townspeople.
家康は江戸城本城の拡張は一定程度に留める代わりに城下町の建設を進め、神田山を削り、日比谷入江を盛んに埋め立てて町を広げ、家臣と町民の家屋敷を配置した。