One of the things Gunma Prefecture is renowned for is its high quality onsens (hotsprings). Among them, Kusatsu Onsen, situated three quarters of a mile above sea level, is considered to be one of Japan’s top three hot spring resorts along with Gero Onsen in Gifu and Arima Onsen in Hyogo.
Kusatsu has the greatest natural flow of hot spring water in all of Japan, much of which surfaces at the Yubatake (hot water field) in the center of town. The sulfurous, highly acidic waters have been credited with curing just about every illness for many centuries. In terms of the quality and quantity of onsen water, Kusatsu remains unrivaled.
Walking toward the center of town, you will notice the characteristic smell of sulfur and see the vapors rising from the drains. The Yubatake itself resembles an emerald green waterfall. Beneath the water’s surface you can catch a glimpse of the white mineral deposits (yunohana) that have formed. The yunohana are prized souvenirs among visitors to Kusatsu, who use the clusters to prepare an onsen bath at home.
Kusatsu’s healing waters can be enjoyed at the various public sento (bath houses) and ryokans (inns) too. The most prominent bath houses are the Sainokawara Rotenburo, the Otakinoyu with its unique Awaseyu baths (multiple wooden baths with different water temperatures) and the Gozanoyu. The onsen water in Kusatsu is around 52˚C and requires cooling before people are able to enter the baths. This is done using a method called yumomi, which involves stirring the water with large wooden paddles. The water is cooled in such a stylized, rhythmic manner that visitors often flock to the Netsunoyu Bath House directly across from the Yubatake to see the Yumomi Performance (湯もみ). There are 3-6 performances per day given by women in traditional dress singing folk songs while cooling the onsen waters. There is a small charge of ¥500 for adults and ¥250 for children to see the performance.
Of course, visitors do not need to go to a bath house or ryokan to enjoy the onsen water. There are ashiyu (foot baths) found in town that can be used free of charge by tourists. One of the foot baths is located next to the Yubatake, while another one is just outside the bus terminal building.
If you get hungry, try the onsen tamago, a poached egg cooked with the hot onsen water. It has a unique texture and is definitely worth trying. Kusatsu is also famous for its onsen tamago flavored soft serve ice cream. For those preferring a sit down meal, there are various restaurants and izakayas (an informal Japanese drinking establishment that serves food) throughout town as well.
The most convenient way to reach Kusatsu Onsen from Tokyo is via the limited express train from Ueno Station. The train travels as far as Naganohara-Kusatsuguchi Station from which point you will need to take one of the JR buses to Kusatsu Onsen.
Web page: http://kusatsuonsen-international.jp/en/