Goshiki Onsen

Onsen in Niseko

At the base (750m) of active volcano Iwaonupuri, Goshiki Onsen has soaring views from the outdoor baths and sulphur-rich, highly acidic (pH 2.6!) waters. It's attached to a deeply rustic ryokan, but most visitors just come for the baths. You need a car to get here; some lodgings do excursions to the baths.