Najima Castle was located on a peninsula projecting into Hakata Bay on the north of the estuary of the Tatara River. The castle fundamentally consisted of the "hon-maru", the "ni-no-maru", and the "san-no-maru", respectively ranging from west to east, and extending for over 900 metres (2953 ft) ("maru" is here a term referring to a space within a castle's grounds). Built by Kobayakawa Takakage, an illustrious Japanese general, it was an impregnable castle. However, when the aspects of politics and economics were considered, it turned out to be undesirable as the administrative centre of the province, for it seemed impossible to construct an extensive castle town because of the river on the south, the sea on the north and the west, and the foothills on the east. On top of that, the castle was located far from Hakata, a large business centre.