Fukushima’s Extreme Onsen Tour will take you on a journey to a wild hot spring to explore the origins of authentic natural onsen.
The Adatara Mountain Range is home to the natural roots of many onsen. In fact, the onsen waters of this mountain range feed the renowned Numajiri and Nakanosawa Onsen. You’ll take a 40-minute guided hike into the untouched Adatara wilderness where you will find a hidden hot spring. This hot spring pumps out 12,000 liters of 80°C water per minute, enough to fill 67 bathtubs. Here, the scalding-hot water of one of the biggest hot springs in Japan mixes with small streams nearby, cooling it to a comfortable temperature while creating dozens of outdoor onsen, called Yatenburo.