Ancient castle ruins in Western Japan. Rows of stones arranged on mountain slopes in Kyūshū 九州 and Western Japan, including six locations in Fukuoka Prefecture, two in Saga Prefecture, one in Yamaguchi Prefecture, two in Okayama and one in Aichi Prefecture. The literal meaning of the term, "stone harboring deities", derives from the pre-Meiji theory that the stones marked a sacred area. However, excavations from the late Meiji period determined hem to be the vestiges of early mountain fortifications dating back to the 5th-7th century. At Otsubosan おつぼ山 kōgo-ishi, Saga Prefecture and Iwakisan 石城山 kōgo-ishi, Yamaguchi Prefecture, it has been shown that the stones originally supported an earthen embankment *dorui 土塁. The rectangular stones are generally found about 300 m up the mountain slope, aligned in a row and surrounding the top of the mountain. At Kōrasan 高良山 kōgo-ishi, Fukuoka Prefecture, the size of the stones is about one-meter long, 70 cm high and 80 cm thick. These walls are similar to fortification ruins on the Korean peninsula and they date from the period when commerce with Korea flourished. Thus it is possible that Korean immigrants played a role in their construction.