An onsen theme water park with slides, hot tubs, and green tea and sake baths!
Opened in 2001, Yunessun in Hakone National Park is more like a hot spring theme park than a traditional onsen; covers 140,000 square meters. The main half of the complex, Yuutopia, requires all of its visitors to wear bathing suits. This creates a pool environment, it is ideal for families as the sexes are not separated. This area has 20 different baths: barrel baths, stone baths, and pools made from Japanese cypress wood, as well as hot tubs and water slides. There are even green tea, coffee and red wine baths; It is supposed to apparently have therapeutic qualities!
The other part of the complex, Mori-no-Yu, is a conventional Japanese onsen with indoor and outdoor baths and a sauna. Bathing suits are not allowed here.