Dogo Onsen

Dogo Onsen claims the title of Japan's oldest hot spring, with its iconic 1894 bathhouse featuring three wooden stories that directly inspired Studio Ghibli's Spirited Away. The main building draws 800,000 visitors annually, 15% more than #7 Gero's totals, thanks to its 42°C alkaline waters that have been flowing for over 3,000 years. The waters contain 0.3 grams of sodium per liter, making them gentler than the average onsen but still effective for joint pain relief. Visitors can ascend to the Emperor's Bath, a private chamber last used by royalty in 1958, for a ¥1,600 fee that includes premium tea service.