Destination Guide · Japan
By Rene L. Diaz, Hydrogeologist · Updated July 2026
Japan has more officially registered hot spring resorts than any other country in the world. The national geological survey has identified over 27,000 natural spring sources, and more than 3,000 locations qualify as registered onsen under the Hot Spring Law of 1948 — a piece of legislation that legally defines what constitutes an onsen by temperature (above 25°C) and by the presence of one or more of nineteen designated minerals or compounds.
The cultural tradition is older than the law. References to communal hot spring bathing in Japan appear in texts from the 8th century. The relationship between hot springs and Japanese culture runs through architecture (the ryokan, an inn format designed entirely around the bathing experience), language (onsen, yu, rotenburo each describe distinct types of bath), seasonal practice (outdoor baths are a specific pleasure in winter, when the thermal contrast is at its most extreme), and even wildlife (Jigokudani in Nagano is renowned for wild Japanese macaques who have used the thermal pools for decades).
Understanding the different formats of onsen helps match expectations to reality.
Kyushu sits directly over one of Japan's most active volcanic systems. Beppu, on the east coast, produces more geothermal water than any city in Japan — eight distinct spring types emerge within a small area, known collectively as the "Eight Hells." Kurokawa Onsen in Kumamoto prefecture is a village of 30 ryokan, all built into a forested river valley, preserving a pre-modern atmosphere rarely found at more accessible destinations.
Hakone is the most accessible onsen destination from Tokyo — 90 minutes by Romancecar express from Shinjuku — and offers views of Mount Fuji from outdoor pools. Takaragawa Onsen in Gunma prefecture is a two-hour drive from Tokyo and worth every minute: its large outdoor pools on the Tone River are among the most atmospheric in Japan, surrounded by ancient forest and open year-round.
Japan's northeastern Tohoku region has some of the country's most remote and traditional onsen. Nyuto Onsen in Akita prefecture is a cluster of seven historic inns deep in a beech forest, each with its own spring and no vehicle access. Ginzan Onsen in Yamagata, with its gaslit wooden ryokan lining a river canyon, is frequently cited as the most visually intact onsen town in Japan — and the model for the setting of the film Spirited Away.
Japan's northernmost island has onsen at every scale, from the large and amenity-rich resort complex at Noboribetsu (which sits above a volcanic caldera known as Jigokudani — Hell Valley — distinct from the Jigokudani Monkey Spa in Nagano) to the wild coastal springs of the Shiretoko Peninsula, which is UNESCO World Heritage listed. Winter onsen in Hokkaido, with snow on the rocks and steam over dark water, is an experience with no equivalent anywhere else in the world.
Kinosaki Onsen on the Sea of Japan coast is a town built around seven public bath houses — visitors stay at ryokan, dress in yukata and wooden geta sandals, and walk between the baths in the evenings. Arima Onsen in the hills above Kobe is one of Japan's oldest onsen, with two distinct water types: kinsen (golden water, iron-rich) and ginsen (silver water, carbonated and radium-bearing).
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