The Japanese macaques of Yudanaka are also called snow monkeys. They love to sit in the hot springs in winter. But still in the 1950s, the monkeys were not doing well. They did the same in the nearby onsen and went straight to the hot baths with the guests. This was not for everyone, so the macaques were hunted first and their population shrank accordingly. But the locals found a compromise - they fed the monkeys an hour upstream through the hell valley at a hot spring, founded the Jigokudani Monkey Park here, where the monkeys now have their own pool, and created one of the most original tourist attractions in Japan. It goes without saying that you make your way through the Höllental at an early hour if you want to photograph the macaques as undisturbed as possible.
When you return frozen from the hike and have chosen in a nice ryokan to stay, you can warm up there in your own onsen. We found a very nice ryokan here, the Yudanaka Yumoto, where we stayed for a few days. The owner was very friendly and helpful and drove us to the entrance of the Höllental early in the morning and even to the train station on departure. The food was great, the staff extremely friendly and professional and the property's onsen was fed by its own hot spring - perfect for winter stays.
Speaking of - Hell Valley means that this is a valley with volcanic activity, there are more often in Japan.