Kiwanosaku

Kiwanosaku - Credit: Wikimedia Commons

was a late Nara period though Heian period josaku-style Japanese castle located in what is now part of the town of Sakata, Yamagata Prefecture in the Tōhoku region of Japan. Its ruins are now an archaeological site and have been protected by the central government as a National Historic Site since 1932. Read more on Wikipedia

type: ancient site
date from: 8th -10th century AD

Source: en.wikipedia.org