The Hommaru Palace, completed in 1615, served as the official residence and administrative seat of the Owari-Tokugawa clan. Together with the tower walls, the Hommaru Palace was one of the first palace buildings to be declared a national treasure in 1930. In 1945, however, it was destroyed in the air raids of the war. Using existing architectural plans from the Edo period (1603-1868) and other historical resources, the palace was authentically rebuilt in 2018 and thus regained its former glory.
The adjacent Ni-no-maru garden, which was used both privately and officially by the successive lords of Nagoya Castle, was once Japan's largest garden that bordered the living quarters of a prince.