Taga Castle was built in the first half of the Nara period (710-794) as part of a defense line against the Emishi people of the north. Administrative work and military planning at the walled-in provincial office would have been occasionally interrupted by attacks. Eventually the dominant Japanese empire would conquer the entire north and set their sights on Hokkaido.
Now the castle ruins are a historic park. Given its large size it is easy to spend an hour or two looking at everything, though don't expect to see more than traces of history you'll have to piece to together with some imagination. Signs in Japanese and simple English tell you what you are looking at. The castle was designated a special historic site in 1995. Onsite is also the Tsubo no Ishibumi (壺の碑), one of the three oldest historical markers in Japan. Free admission. Open daily. More info in the supporting article here.
