Onsen area, source and facility — what's the difference?

Four layers

This atlas records onsen in four layers.

**Area**: the land where the springs rise and the cluster of inns and shops around it — Kusatsu, Kinosaki. Groups of areas (Okuhida Onsen-go, Nyuto Onsen-kyo) are "districts" and belong here too.
**Source**: a single outlet where water emerges or is pumped. Kusatsu has several — Yubatake, Shirahata, Sainokawara, Bandaiko — each slightly different in temperature and chemistry.
**Facility**: an inn, hotel, day-use bath, communal bathhouse or foot bath that pipes water from a source into its tubs.
**Bath**: each individual tub inside a facility — indoor, open-air, private, in-room. Within one facility, baths may draw on different sources and differ in whether they are free-flowing.

Conversations about onsen become far more precise when you say which layer you mean.

Sharing one source, mixing several

In many onsen towns the inn association owns the sources and distributes the water to each inn — "central supply". Whichever inn you choose, the water is the same. In other places, such as Awara, each inn has its own source, and the water next door can be entirely different.

Tubs sometimes mix two sources to adjust the temperature. In places with many differing sources, like Naruko, changing inns means changing water.

Zhaitengli · CC BY 4.0

Naruko Onsen

鳴子温泉

Miyagi · 100 Onsen to Know Japan — No. 18

SulfurSulfateBicarbonateChlorideSimpleIronAcidic

Seven of Japan's ten official spring types in one valley. The communal Takinoyu by the station costs 300 yen, and the town lends you wooden geta to clatter from bath to bath.

Asturio Cantabrio · CC BY-SA 4.0

Awara Onsen

芦原温泉

Fukui · 100 Onsen to Know Japan — No. 43

Chloride

A spa town in the rice fields where 74 separate sources are owned inn by inn. At the free Ashiyu foot bath by the station you can compare two different waters with your feet.

Aspere · CC0

Kusatsu Onsen

草津温泉

Gunma · 100 Onsen to Know Japan — No. 25

AcidicSulfurSulfateChloride

Thirty-two thousand litres a minute of pH 2.1 acid water rise in the middle of town and cool as they run down wooden channels.

Districts and areas overlap

Okuhida Onsen-go is a collective name for five areas: Hirayu, Fukuji, Shin-Hirayu, Tochio and Shin-Hotaka. Counting both the district and its areas would count the same places twice. This atlas stores districts as a separate kind ("group") and excludes them from the totals. Official statistics also draw area boundaries differently from prefecture to prefecture, so compare numbers with care.

Alpsdake · CC BY-SA 4.0

Hirayu Onsen

平湯温泉

Gifu · 100 Onsen to Know Japan — No. 55

BicarbonateChlorideSimpleSulfur

Some forty sources pour out 8,600 litres a minute, and right by the bus terminal are a donation-only bath and a complex of sixteen open-air pools.

Soica2001 (talk) · Public domain

Shinhotaka Onsen

新穂高温泉

Gifu · 100 Onsen to Know Japan — No. 54

SimpleChlorideBicarbonateSulfur

Look up at 3,000-metre peaks from a riverside open-air bath, then ride a double-deck gondola from the same spot to 2,156 metres.

Which layer to choose by

If you are after the atmosphere of a town or a round of public baths, choose by area. If you want to experience a specific water — radon, carbonation — choose by source and the baths that use it. Solo stays, prices and tattoo policies are facility matters.

Search in this atlas starts from areas, but the facilities tab shows day-use availability and hours per facility. Areas with in-depth articles include tables for each facility and each bath.

Glossary

Onsen district (onsen-kyo / onsen-go): A group of neighbouring onsen areas. A tourism term with no legal definition.
Central supply: A system in which an association manages the sources and distributes water to each facility.