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The Yamagata Basin is a long and narrow inland valley of the Mogami River bounded by the Ōu Mountains to the east. It is an important communications center for the southeastern portion of the Tōhoku region of Japan. connecting the Shōnai Plains and the Sea of Japan to the west with the Yonezawa Basin to the south, and the Sendai Plains and the Pacific Ocean across the Ōu Mountains. In addition to riverine traffic, the route of the Ushū Kaidō highway also passes through the area. Yamagata Castle is located at the southern end of the Yamagata Basin.