Onsen Defined
How do Onsen Work?
Onsen, known in English as hot springs are usually a byproduct of Volcanism.

How many Onsen are there?
Hot springs are much more numerous than people realize.  Many hot spring
would be better called warm springs as they may be just a few degrees
warmer than regular surface water or even cooler. In Japan there are literally
thousands.

Are there hot spring in America?
There are actually many hot spring in the United States, but we have never
developed the passion for them as the Japanese have. New Mexico, Arizona,
Idaho, Wyoming, Colorado, Arkansas, North Carolina, Alaska, California,
Oregon, and Washington all have noteworthy hot springs.


There is a public bath in my neighborhood. Is this an Onsen?

There are 2 main types of public bathing experience in Japan.

Onsen
The Onsen which is naturally heated (maybe) water laden with minerals.  
This type of bating experience is a travel or holiday experience. Onsen are
often associated with an Inn and usually have at least a short order or
counter service cafeteria and sometimes a 5 star restaurant. To get away
from the daily grind of the city and commune with nature. Onsen vary in feel
and use from undeveloped onsen, community sponsored free baths for
locals in a small shed big enough for one, to huge, elaborate multi-bath
amusement parks and everything in between.

Sento
The Sento (public bath) is regular water that has been heated and is a
communal experience where Japanese go to literally shed the layers of
status and relax after work on a regular basis.  The atmosphere is relaxing
but its a bit more boisterous ans family like.  Traditional Sento are easily
recognized by their smoke stacks from the large furnaces.
There are also modern Sento that kind of blur the line between the Onsen
and Sento.

Is this a real Onsen?

There are may types of Onsen in Japan and qualifying one as real depends
on you point of view in some cases.  

Techno Onsen
Some Onsen are technological Onsen. At one little inn I stayed at in Nikko. (a
place known for it's Onsen) The Inn was designed for young  couples and
they had a very nice private outdoor bath that you could reserve.  I asked
where the Onsen source was and the innkeeper explained to me that they
took well water and filtered it through a mixture of rocks and fortified it with
minerals to make it like a natural onsen. The bath was very nice and the
water felt good but I wouldn't personally classify this as a real onsen.  Its
more of a fortified Sento.

Cold Onsen
Another type of Onsen is the kind that comes out of the ground cold or
luke-warm and is artificially heated to a comfy simmering temperature.

Drilled Onsen
There are also Onsen where deep wells are drilled to access mineral laden
water deep under the ground and pump it to the surface.  These are
becoming more common recently and quite a few have sprung up in the
cities. A huge onsen/public bath house was just built near my home in Tokyo
using this method called Utsukushi no yu  My wife and I walked
by it on our daily commute and we argued for the longest time because when
they stared out, it was basically an empty lot. Then they brought in a drilling
rig and I suspected they were building an Onsen, but my wife didn't believe It.
About 6 moths later, I was proved right.
Although I wouldn't classify this as a real onsen either, I was a regular patron.
I couldn't resist, considering it was about 3 minutes from my house! The
outdoor baths were wonderful with 3 little baths connected by a flowing
cascade set in natural slate surrounded by little Japanese maples and other
pretty greenery and a huge privacy fence. (So the people living in the local
high rises couldn't peek.)
The only drawback was you could hear the nose from the pumps and other
machinery from the bath which kind of ruined the mood a bit. The crowds at
certain times of the day could turn off some people too.
I sometimes wondered how clean the water was. Questions like how long the
water was recycled before adding new water, and how much they had to heat
the water often ran through y mind. I usually rinsed off in the shower after I
was done soaking, just for peace of mind.

Gourmet Onsen
For me, a real Onsen is one where the water is comes out of the ground,
flows into the baths without being heated, and then flows out.  This is actually
the thing I like best about natural Onsen is that the water is always being
renewed.  Keeps the human soup to a minimum.  My favorite Onsen are
Rotenburro (Outdoor baths) that smell a bit of brimstone and have a
beautiful view of nature.


Diary of an Onsen geek
Trying new Onsen can be epic. One good adventure I had was at a little
hiking hut in the mountains near Okutama.  It showed an Onsen on the map
so I rode my bicycle to the trail head and then hiked to the Hut. I paid my fee
and went in.  The bath turned out to be a very traditional  ceramic tub which
was filled daily from a cold spring and heated with a wood stove. (Its called an
Onsen because of the mineral content.) I washed off as well as I could with
cold spring water and got in. I immediately regretted it.  Not only was it not hot
enough, but it smelled like wet hiker, (A smell similar if not worse that wet
dog.) and was infused with little curly hairs floating everywhere. I stuck it out
and soaked for 10 or 15 minutes then got out and tried to rinse off with the
freezing cold spring water. I went home and took a bath. I think this could
have been a nice experience if I had soaked in the morning and not in the
high season after 200 hikers used the bath that same day. I arrived 5
minutes before closing, so thats probably why the water was cool and a bit
nasty.  I'm sure they clean the bath daily and it probably wonderful first thing
in the morning if you are staying at the hut. I would recommend a visit if you
are hiking Kumotoriyama and looking for a hut to stay at.  The hut was
classic and the surrounding scenery was beautiful.


ONSEN
Basic Information
Sanjo no yu 三條の湯
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