Kii Castle

Its ruins have been protected as a National Historic Site since 1937, and raised to a Special Historic Site since 1954. After the defeat of the combined Baekje and Yamato Japan forces, at the hands of the Silla and Tang China alliance at the Battle of Hakusukinoe in 663, the Yamato court feared an invasion from either or both Tang or Silla. In response, a huge network of shore fortifications was constructed throughout the rest of the 600s, often with the assistance of Baekje engineers, generals and artisans. Unaware of the outbreak of the Silla-Tang War (670–676), the Japanese would continue to build fortifications until 701, even after finding out that Silla was no longer friendly with Tang. The name "kōgoishi" means "stones of divine protection," a name given them by the Meiji period archaeologist Tsuboi Shōgorō, who conjectured that they served as spiritual or practical protection for sacred sites. Scholars after Tsuboi determined that the structures are most likely the remains of practical, military fortifications, and were unlikely to have significant spiritual connections, although much remains unknown about these structures and there is very little contemporary documentary evidence. Kiyama Castle is located approximately eight kilometers south of the Dazaifu Government Office ruins, overlooking the branch point of the ancient government highway connecting Dazaifu with Higo Province and Chikugo Province. Kiyama Castle surrounds the eastern summit of Mount Kiyama, with fortifications at an elevation of 404 meters.