Enjoy a fascinating stroll through Sainokawara Park 西の河原公園 in Kusatsu Onsen in the Gunma Prefecture. The emerald green hot spring water which makes the town famous bubbles to the surface in many places throughout the park, forming pools and rivers and even a waterfall. It all takes on a surreal appearance on cool days when steam rises from the waters, but is beautiful throughout the year.
In addition to the park itself, there is a very nice outdoor onsen bath at Sainokawara Park. There are two large pools, one for men and one for women, filled with the natural water with its reputed medicinal value. Each bath holds about 100 people. The baths are open from 7 am to 8 pm from April to November, and 9 am to 8 pm from December to March. Adult admission is 500 yen and admission for children is 300 yen.
Sainokawara Park is about a 10 minute walk toward Mt. Shirane from the yubatake in the heart of Kusatsu Onsen. The street is lined with small shops and restaurants which are also fun to explore.
Address: 521-3, Kusatsu, Kusatsu-machi, Agatsuma-gun, Gunma
The website is only in Japanese but has some lovely pictures! http://www.sainokawara.com/