Gensen kakenagashi

Gensen kakenagashi (literally "source water flowing") is the highest grade of Japanese onsen, the water comes directly from the natural hot spring, flows continuously through the bath, and is never recycled, heated artificially, diluted, or chlorinated. About 30% of Japan's onsens qualify for this designation. What to look for: the term "gensen kakenagashi" displayed at the entrance, often with a certification label. The water quality is noticeably different, softer on skin, more mineralized, sometimes naturally colored (white, green, brown). For a true onsen pilgrimage, target ryokans (traditional inns) advertising gensen kakenagashi private baths. Costs at premium ryokans: 400-1,200 EUR per night including dinner and breakfast. Booking 3-6 months ahead is essential for top properties.