In the northern part of Tochigi prefecture two or three hours north of Tokyo, Kinugawa Onsen is a popular hot-spring resort town, surrounded by dramatic hills, and built along a river that's carved a steep gorge into the land.
It's heavily developed, and the river is lined in places by towering resort hotels, some of which have onsen (hot-spring baths) that are open to the public; the staff at the station's information desk can make suggestions and provide some discount coupons. That part of the town isn't so attractive, but I enjoyed bathing in the onsen, and the hotel I went to had a very well-stocked gift shop. I imagine the others do too.
The less developed part of town has better scenery: it's possible to follow a path that follows the course of the river, though the water is far below you at the bottom of the gorge. This path takes you to the enjoyable Tateiwa Otsuribashi, a suspension bridge that's fun to walk across, and gives a good view of the river.
If your feet are weary from walking but you don't have the time or inclination for an onsen, in front of the station there's a free little foot spa. You can soak your aching feet here before catching your train or retiring to your hotel.