Furutōbe Onsen, Ikarigaseki
A lone hidden spring at the end of a forest road in the hills of Ikarigaseki, Hirakawa, near the Aomori–Akita border. Famed nationwide for its gushing flow — said to be 500 litres a minute — the overflow from the tub streams across the entire washing floor like a river, and the place once topped a fan vote for the best free-flowing bath in Japan. The sodium-calcium-chloride-sulphate water is pale yellow-brown with an iron tang, and the local way to enjoy it is 'todo-ne': lying flat on the floor and letting the running water wash over you like a sea lion. After a long closure it reopened, renovated, in December 2025: day bathing adults ¥600, children ¥200, 09:00–20:30. Lodging is bed-and-breakfast or room only. Pick-ups from Ikarigaseki Station and Yunosawa can be arranged (contact in advance). Facilities are basic and days and hours can change, so check by phone or on the official social media. About 15 minutes by car from JR Ikarigaseki Station or Ikarigaseki IC; beware of deep snow in winter.