There have been humans on Mount Zao for at least 1,900 years. While the onsen town’s beginnings are uncertain, the properties of its waters are well known. Therapeutic and invigorating, with names like “springs of beauty,” these hot springs brought an influx of tourism in the early 1900s. The water of Zao Onsen is very acidic, with a pH range between 1.6 and 1.25. This acidity offers a variety of medicinal benefits, but it will also oxidize and discolor metal, so visitors should take care with any jewelry or piercings. Zao has three famous hot springs, all of which are open to the public for a small donation of 200 yen.
As these springs are very old, traditional facilities, it is important to know the correct behavior for visiting one. The hot springs are separated: one side for men (男), and one side for women (女). Visitors must bathe before entering the bathhouse. There is no space to wash in the bathhouse itself and entering a communal bath without washing is considered impolite. Towels are not worn into the water; some bathers place their towels on top of their heads but leaving it by the edge of the bath is also fine. Smoking or roughhousing within the baths is also prohibited. Because of their association with crime, tattoos are considered taboo within Japanese society, and visitors with tattoos are asked not to enter the bath.
