Nasu, where I live now, is a famous resort area with a lot of fun. One of the popular attractions here in Nasu is Onsen, or hot springs.
Most of the traditional ryokan ( Japanese style Inn) has traditional bath tab with Onsen water from fountain of mountain. If you are interested in trying it, you can reserve a onsen ryokan here, then you can fully enjoy the onsen with a full course dinner also in Japanese style. As usually meals for dinner and breakfast are included, price for ryokan is higher than standard business hotels in Japan.
Onsen is know as public bath. And many from overseas don't like it for the first time because they need to be naked while taking the bath together with other people. The Japanese are naturally trained for the custom of naked bathing becuase we usually are brought to onsen by our family when we are little kids.
In Nasu, just like standard Onsen places, there are some public bath also outside the ryokan. The bath house is just for bathing only, so you can't stay there. Addmission is cheap. For example, at Shikanoyu, the most famous and oldest public bath house in Nasu, we just pay about 400 yen ( about 5 dollars ) per person.
Shikanoyu is a really old bath house as you see photos. It's located near the river, and building is a really old wooden house. It's a kind of nostalgic experience for me to go there because this type of old bath house is no longer existing in many of the cities of Japan. It's still clean but you might not like it if you are accustomed to modern bathroom at your home.
Surrounded by mountain with beautiful trees, we can enjoy a relaxing time of Onsen in Nasu. If you are nature lover, Nasu is a good choice. Also onsen experience is one of the traditional Japanese culture we still have. It might be nice for you too if you are brave enough to check it out.