Visitors to those European spas and others immerse themselves in healing, briny water containing a minimum of 1.45 percent salt. The salt springs on which the spas are built are found nearly everywhere in Germany.

"Developing them is very expensive and so is using them," says Professor Karl-Ludwig Resch of the German Institute for Health Research in Bad Elster. Thus, there's little wonder that for centuries salt commonly has been known as "white gold".

Salt mining was in many places the basis for prosperity before the existence of the spa and recreation operations were built near salt springs, says Werner Schmidt of Hohenlohe, a district in northern Baden-Wuerttemberg, and a spokesman for a tourism company.

"Beyond its use in spas, salt no longer plays an economic role," says Schmidt. But recreational enthusiasts follow the tracks of salt's story when they travel the "Salt and Brine Wellness Route" in the Swabian Alb region northward to between the Neckar and Hohenlohe districts where there are abundant underground salt deposits.

Bathing in salt water can lift one's well-being. Water containing 3 percent salt gives the body buoyancy, allowing the muscles to relax. The higher the salt content in the water, the greater the relaxation.

"As opposed to meditation, you don't need a concentration technique," says Resch. A good floating sensation can be achieved in water that is 7 percent salt, and near weightlessness can be felt in water that is 15 percent salt. While bathing in water with these high concentrations of salt, the automatic nervous system cuts back and the person is fully relaxed.