(The construction of `Kogo-ishi yama-shiro mountain castle,' ancient mountain castles, were not recorded in the history books of the Yamato Kingship, and they were located from northern Kyushu through to the coastal regions of the Inland Sea lying between the islands of Honshu and Shikoku, and most of Kogo-ishi yama-shiro mountain castles were also concentrated in northern Kyushu).
（またヤマト王権に建設の記録が無い古代山城「神籠石（こうごいし）式山城」が北九州から瀬戸内沿岸に存在するが、神籠石式山城の大半も北九州に集中している）。