Kusatsu is a popular resort in Japan. The reason for the fame can be found in the surrounding mountains: Directly behind Kusatsu is the 2.160 m high Kusatsu-Shirane-san and less than 30 kilometres further south of the Asama-yama. Both are active volcanoes with recent eruptions.
Such a geologically active zone brings pleasant side effects: onsen – hot springs. Especially in Kusatsu at the foot of the mountains, a lot of hot water comes out of the ground. The hot springs of Kusatsu have two special features: On the one hand, the water is very acidic in terms of the pH value, on the other hand extremely hot – the outlet temperature is 45 to almost 95 degrees Celsius, depending on the source.
While in most spas with hot springs in Japan it must be drilled more or less deep into the ground, in Kusatsu you can splurge: in the middle of the city, the steaming water bubbles out of the ground and from there over a network of wooden frames. The whole thing is called Yubatake (hot water field). These are also available elsewhere, but not as large and centrally located as in Kusatsu. By means of the frames, the yunohana (hot water flowers) are virtually "grown." These crystals consist largely of sulfur and are later sold or used in other onsen, for example as a bath additive.
In addition to bathing, the water from the onsen is also used for heating the primary and secondary school, the municipal welfare centre and the swimming pool.