Ōtoriiyama ruins 大鳥井山遺跡

Ōtoriiyama ruins 大鳥井山遺跡 - Credit: Wikimedia Commons

The is an archaeological site containing a large Heian period jōsaku-style fortification located in what is now part of the city of Yokote, Akita in the Tōhoku region of Japan. The site was designated a National Historic Site of Japan in 2010. Read more on Wikipedia

type: military installation
date from: Heian period

Source: en.wikipedia.org