Kusatsu Onsen, Thermal hot spring resort in Gunma Prefecture, Japan.
Kusatsu Onsen is a thermal spring resort in Gunma Prefecture, Japan, known for its highly acidic waters. At the center stands the Yubatake, a large wooden structure of chutes through which hot spring water flows at around 55 degrees Celsius (131 degrees Fahrenheit), sending clouds of steam across the surrounding streets.
German physician Erwin von Baelz visited the site in the late 19th century and documented the healing effects of the acidic springs, leading to their recognition in Western medicine. Travelers and wanderers from across Japan had already been seeking out the thermal waters for centuries to treat skin ailments and muscle pains.
The Netsunoyu hall hosts daily demonstrations of yumomi, an old method in which performers use wide wooden paddles to stir and cool the thermal water while singing folk songs. This practice developed because the water would otherwise be too hot, and today it combines practical necessity with communal ritual.
Direct buses connect Shinjuku station in Tokyo to the resort in roughly three hours, with additional connections available from Naganohara Kusatsuguchi station. The site sits at over 1,200 meters (around 4,000 feet) elevation, so visitors should pack light jackets even in summer, as evenings can turn cool.
The natural springs deliver the highest water volume among all hot springs in Japan, with more than 32,000 liters (around 8,500 gallons) emerging per minute. The high acidity of the water acts as a powerful antibacterial agent, which is why the springs have long been valued for their cleansing effect.
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