Onsen is a Japanese term that refers to hot springs and the bathing facilities and traditional inns around them. Onsen may be either outdoor baths or indoor baths, and traditionally, onsen were located outdoors, although many inns have now built indoor bathing facilities as well. Nowadays, as most households have their own baths, the number of traditional public baths has decreased, but the popularity of sightseeing hot spring towns has increased. There are approximately 25,000 hot spring sources throughout Japan, and approximately 3,000 onsen establishments use naturally hot water from these geothermally heated springs.
The water in onsen is heated by the earth and contains minerals that can make the experience totally different from other types of baths. Onsen water is geothermally heated beneath the ground and rises to the surface bubbling hot. The prerequisites of an official onsen are that the water must contain at least one of the 19 designated chemical elements that naturally occur in hot spring water, and it must be at least 25C when it comes out of the ground.
Onsen can be either publicly run by a municipality or privately, often connecting to a lodging establishment such as a hotel, ryokan, or minshuku. The presence of an onsen is often indicated on signs and maps by the symbol ♨, the kanji 湯 (yu, meaning "hot water"), or the simpler phonetic hiragana character ゆ (yu) .
In summary, onsen is a Japanese term that refers to hot springs and the bathing facilities and traditional inns around them. Onsen may be either outdoor or indoor baths, and the water is heated by the earth and contains minerals that can make the experience totally different from other types of baths.
