Yunohana Chaya Shinzaemon no Yu

Zao Onsen is said to have been founded 1,900 years ago and is known as the oldest hot spring in Yamagata Prefecture. With some of Japan’s most strongly acidic waters, its sulfur-rich spring is valued for its antibacterial properties and is expected to help ease symptoms such as cuts, burns, and atopic dermatitis. It’s also said to promote circulation and support healthy-looking skin, and has long been known as a “beauty hot spring.”

Enjoy 100% natural hot spring water straight from the source, plus a selection of gentler baths such as Yon-Roku no Yu and Kameyu for those with more sensitive skin. Soak it all in in the forest-surrounded open-air bath or indoor baths.

There’s also a dining area and a souvenir corner to round out your visit after a soak. At the restaurant, you can enjoy local favorites like 100% buckwheat soba (juwari soba) and sukiyaki set meals made with Zao Beef, a brand of wagyu raised in the area. The souvenir corner is stocked with Yamagata specialties.

In April 2023, the facility launched a reservation-only sauna. You can set the temperature up to 248°F and do self-service löyly with your choice of three aromas—an easy favorite among sauna fans.