Tucked above the gorge on a forested slope, Hoheikyō is Hokkaido's largest outdoor bath and it feels like a magnificent secret. The whole rambling structure is gloriously shack-like, with steam curling through cedar beams and the scent of sulphur mingling with mountain air. You'll soak while gazing at a canopy of trees that turns electric crimson in autumn. The gender-assigned baths swap daily, so you'll get a different panorama each visit. Repeatedly voted the best onsen in all of Hokkaido, and it absolutely earns that title.