Kamikawa, Kamikawa District, Hokkaido
Rating
Cost per person
Free
Yūdoku Onsen, or "Poisonous Hot Spring," is a unique and inaccessible hot spring located in the Ōhachidaira crater of Daisetsuzan National Park, Hokkaido. Due to the high concentration of volcanic gases like hydrogen sulfide and sulfurous acid gas, access to the central part of the crater is strictly prohibited due to the risk of poisoning and asphyxiation. While you can't bathe in it, the hot spring can be viewed from the trails along the rim of the crater, offering a dramatic and toxic landscape. The best views are from the traverse routes of Mt. Asahi-dake to Mt. Hokuchin-dake to Mt. Kuro-dake, or Mt. Asahi-dake to Mt. Kitakai-dake to Mt. Kuro-dake. For those interested in a soak, consider the Naka-dake Onsen, a foot bath along the trail from Mt. Naka-dake to Sugatami Ropeway Station.