Rich in active gases or metals — a strong mineral character.
Buoyancy
Standard buoyancy
LowHigh
Soft water — natural, classic buoyancy.
Radioactive fluorée sodique
At Caldas do Gerês, in northern Portugal, radon-bearing water emerges at 45°C within Peneda-Gerês National Park. The thermal facility sits amid rivers and hiking trails, in a reserve home to garrano ponies and wolves, close to the Spanish border.
Insider tip — The garranos (small semi-wild horses of Gerês) sometimes bathe in the same waters as the spa-goers.