Running through a 15-mile-long ravine, Route 39 cuts through the northeast entrance of Daisetsuzan National Park. For 5 miles, sheer cliff walls rise on both sides of the canyon as the road drills into the mountains. In winter and early spring, forbidding stone spires loom as if in judgment; in other seasons they thrust through glorious foliage. On the way there are a couple of river-carved gorges called Obako and Kobako, which are pretty, but underwhelming if you've seen really gorgeous gorges before. Go see Momijidani (Maple Tree Valley) if you're here in autumn.
Soun-kyo Onsen village is halfway through the ravine. In summer, the pedestrian-friendly main street is lined with flower boxes, and guesthouses and souvenir shops add charm to what is basically a concrete version of an alpine village. Most activities take place outside the village, so while people are hiking through the park the village feels dead. From Late January to March, the frozen river and its ice cliffs are illuminated for the Ice Waterfall Festival, which is breathtaking. If you're driving, watch your gas tank, as there is no gas station in town.