Kusatsu Onsen is a hot spring resort town in the mountains of Gunma Prefecture. Its spring is famous for both its prodigious daily output and its high sulfur content, which makes the entire town smell of rotten eggs but is said to cure a host of bodily ills. In fact, the locals say the hot springs in Kusatsu cure any sickness but love sickness.
Whatever its healing properties, you wouldn’t want to jump into the spring at the source, as it comes bubbling out of the ground at up to a scalding 95°C (203°F). You could add cold water, but that would dilute the beneficial mineral content, so the locals use a traditional method called yumomi, which involves splashing the water around with big tongue depressors while singing and dancing.
I love Japan.