Naruko Onsen Mudpots

They are part of the geothermal landscape around Naruko Onsen in Osaki, Miyagi Prefecture, in Japan's Tohoku region. The wider area includes bubbling geothermal features, acidic waters and several historic hot-spring districts. [Tohoku Tourism](https://www.tohokukanko.jp/en/attractions/detail_1206.html)

Underground heat and geothermal gases push water and fine mineral-rich mud toward the surface, producing the bubbling effect. They are natural geothermal features, not ordinary pools of wet soil or prepared bathwater. [Japan National Tourism Organization](https://faq.japan-travel.jnto.go.jp/en/destinations/tohoku/miyagi/naruko-area/)

The mudpots should be treated as observation features rather than bathing pools, unless local authorities explicitly allow access. Visitors who want to bathe can use designated facilities such as Taki-no-Yu, a traditional public bath near Naruko Onsen Station. [Naruko Tourism](https://www.naruko-roman.jp/)

Katanuma is a strongly acidic crater lake with a circumference of about 1.3 kilometers, while the mudpots are smaller bubbling geothermal vents. Katanuma is roughly 10 minutes by car from Naruko-Onsen Station. [Tohoku Tourism](https://www.tohokukanko.jp/en/attractions/detail_1206.html)