Yutopia

ラドン温泉ホテル 湯ーとぴあラドンおんせんホテル ゆーとぴあ

Lodging
Chubu·Yamanashi

Day Use

Yes

Bathing & Water

OnsenYes

Uses natural hot spring water

竜王ラドン温泉

Ryuo Radon Onsen

Operated by · 株式会社 湯ーとぴあ

Sampled at wellhead
Chloride
+ Bicarbonate
Classification

Sodium Chloride spring

A sodium-led chloride spring with bicarbonate softness layered in. Weakly alkaline and soft on the skin, it sits in the Japanese beauty-water family. The water carries a faint yellow-brown tint, a slight salty tang, and a faint hydrogen sulfide note, and the source also bears a small amount of radon.

pH
8.00
Weakly alkaline
Source temperature
39.4°C
Warm
Tonicity
1.39g/kg
Hypotonic
Flow rate
130L/min
Typical
Free CO₂
521mg/kg
Typical
Radon
2.76Bq/kg
Low
Color
faintly yellow-brown and clear
Taste
slightly salty
Odor
faint hydrogen sulfide

Analyzed Sep 10, 2019·株式会社メイケー·Cert no. M19-3020

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SM
Sergey M
1 year ago

544. Yutopia, Kai, Yamanashi A wild hotel with a radioactive onsen. In the lobby there's some kind of crazy machine, a large cage with a sleeping cat, and a shop selling retro stuff. Visited for higaeri at 880. Higaeri hours are listed as 10:00 to 23:00. They stamp the Yamanashi 100 Onsen book. Bath photos are from the internet, match the real thing. 1. Indoor area. Breathing inside is good. 1.1. Bath with clear slightly yellowish water. Has utaseyu. Temperature around 39-40. 1.2. Cold bath. 2. Indoor area within the indoor area. There's a separate staircase and a sealed door leading to the radioactive section of the onsen. Inside, everything is covered with posters in Japanese, one of them has a medical "+" symbol. Inside there's a bath with clear slightly yellowish water, temperature around 40, with occasional individual bubbles. It's stuffy inside. I think the onsen at Black Mesa in Half-Life looked exactly like this. Very unusual, strange place. For people with radiophobia — better stay away. 11.05.2025