The Ni-no-maru secondary bailey contained the palace of the daimyō of Karatsu and the domain’s administrative offices.

Records indicate that a stone foundation base existed from at least 1627, but the Tokugawa government never authorized the construction of a donjon tower.

In the Battle of Sekigahara in 1600, he joined the forces of Tokugawa Ieyasu and attacked Gifu Castle.

The Tokugawa shogunate ordered neighboring tozama domains to contribute to its construction, and they did so primarily by excavating its network of moats.

The current donjon features five tiers and five stories, with a lower ground floor; it also houses an exhibition area.