Ōshū Kaidō
Ōtawara Castle was built by Ōtawara Harukiyo's grandfather, Ōtawara Sukekiyo, in 1545 on a 25-meter high hill overlooking the Sabigawa River. The main gate of the castle faced west, and fronted on the Ōshū Kaidō, the main highway linking Edo with the northern provinces of Japan. The castle consisted of a northern kuruwa, followed by the main bailey, second bailey and third bailey.