Radium Onsen Hoyo Center
Edogawa, Tokyo, Japan
Illustration photo — not a verified picture of this exact spot.
- Location
- Edogawa, Tokyo, Japan
- Water type
- radioactive
- Temperature
- 38 °C
- pH
- 7.3
Water profile
Thermicity
Neutral
LowHigh
Soothing — neither hot nor cold, perfect balance.
Mineralisation
Bio-active
LowHigh
Rich in active gases or metals — a strong mineral character.
Buoyancy
Standard buoyancy
LowHigh
Soft water — natural, classic buoyancy.
RadonLithiumBicarbonates
Hoyo Center, in Tokyo's Edogawa ward, offers radioactive (radon-bearing) water at 38°C, a type long valued in Japanese onsen tradition. Indoor bath, outdoor rotenburo and sauna round out the facility.
Insider tip — Radium Onsen Hoyo Center serves Edogawa Ward in eastern Tokyo as one of the few genuine urban radon springs in the metropolitan area. The Edogawa spring was discovered during post-war well-drilling and has served the working-class communities of eastern Tokyo as an affordable alternative to remote mountain thermal resorts since the 1950s — an urban marvel of natural geothermal energy beneath one of the world's most densely populated cities.
Nearby
Frequently asked questions
How hot is the water?
The water is neutral here, around 38 °C — a perfect balance, neither too hot nor too cold.
What type of water is found here?
This spot features radioactive water.
What is the best season to visit?
The most favourable period for this spot is: Toute l'année.