Misasa Onsen Kiya Ryokan

A 14-room wooden inn listed as a cultural property, with its own very hot radium springs — a free private bath where the water bubbles up through the floor, a radon steam room and a warm-floor rest room — but expect stairs, stink bugs and simple, home-style food

Kiya Ryokan took the trade name of an Edo-period village headman's house and became a full-time inn in 1868. Its Meiji, Taishō and Shōwa wings, joined over the years into a maze of steep stairs, were listed in full as a Registered Tangible Cultural Property in 2010. There are 14 rooms on three floors and no lift. The draw is the water: the inn's own radioactive sodium chloride springs (56–80°C, pH 7.2), all free-flowing. In the private Rakusen-no-yu the spring bubbles up through stones in the floor, and there is a drinking fountain beside it. There is also a second private bath from the Taishō era, separate baths for men and women, a paid radon steam room and a warm-floor room for lying down in your yukata. Japanese guests rate it 4.8 across 400 reviews on one major site, 4.32 across 244 on another (baths 4.64) and 4.56 on a third (baths 4.92). Bloggers in 2023–2024 called it the best and most potent water they had tried. Others praised the in-room dinners, including a stew baked inside a bread 'pot', and staff who explain each bath. Complaints are dated and mostly minor. The springs are so hot you must add cold water, and the floors can burn your feet (2023). Stink bugs got into rooms in February–March 2026, and the car park is hard to find. One May 2026 reviewer found the menu unchanged for months and the staff calls over the PA system intrusive. The private baths are often taken. Basic plans start at ¥18,700–24,200 per person on weekdays, and in 2026 people paid about ¥19,000–29,000.