Tamagawa Onsen

What to know

Tamagawa Onsen (玉川温泉) is a unique hot spring resort nestled in the mountains of Towada-Hachimantai National Park. It is renowned for having Japan's most acidic hot spring waters, with a pH level near 1. The area also boasts a rare, radioactive stone called hokutolite, believed to offer various health benefits, including cancer prevention and treatment. This draws cancer patients from across Japan.

The resort consists of a single ryokan with many simple rooms and a public bath. Guests can stay overnight or visit for a day soak. Unlike typical Japanese hot spring resorts, Tamagawa Onsen attracts a large number of visitors seeking health benefits rather than leisure. However, regular tourists are also welcome. Note that the ryokan is closed during winter, from early November to mid April.

The bathing facilities feature gender-separated, wooden indoor baths with multiple pools. Experienced onsen-goers will immediately notice the high acidity, which can sting sensitive skin or open wounds. Some pools are fed directly from the source, while others are diluted to 50% to reduce acidity. There are also wooden steam boxes for sitting. In winter, the baths are available only to overnight guests.

The hot spring water emerges spectacularly in a valley just a short walk from the ryokan. A single source gushes nearly 9,000 liters of 98°C water per minute, making it Japan's most productive hot spring source. Surrounding it are smaller sources, hissing sulfur vents, and streams of hot water, all viewable from walking paths. Along these paths, you'll see many people lying on the radioactive rocks for hours, seeking health benefits.

The volcanically active valley also serves as the trailhead for a seven-kilometer hiking route over neighboring Mount Yakeyama to Goshogake Onsen, another volcanic area with hot spring facilities. Autumn colors at Tamagawa Onsen are usually best from mid to late October.

Two kilometers down the road lies Shin-Tamagawa Onsen ("New Tamagawa Onsen"), a second ryokan with baths fed by the same hot spring water. Unlike Tamagawa Onsen, Shin-Tamagawa Onsen remains open during winter.