West of Iide Town and Yamagata's largest municipality, Oguni Town takes up roughly one seventh the area of the prefecture, most of this being mountainous. The Yoko-kawa (Yoko River), Tama-gawa (Tama River) and other rivers flow from mountains in the north, east and south to feed the Ara-kawa (Ara River) which heads west into neighboring Niigata Prefecture before reaching the Japan Sea. Although Oguni actually lies in Niigata Prefecture's drainage basin, because of historical and geographic reasons it is now part of Yamagata. The geographic reason is particularly noticeable even today: while the eastern pass to the rest of Yamagata is not that high, the narrow canyon on the Ara-kawa near the Niigata border was only opened up to regular transportation fairly recently.
All of the above factors--rivers, mountains, canyons--make Oguni not only a hiking paradise, but also great for stream fishing, wild vegetable gathering, camping, etc. The town is also famous for its huge tracts of virgin beech forests which have been designated for permanent protection. Oguni even has several hot springs, perfect for soaking in after a long day in the mountains.