A visit to hot springs for relief of physical disorders represented the earliest therapeutic applications of water.

The techniques employed then included sitting in tubs of water, hydrosudotherapy (sweat baths), and baths in hot water heated by coal fires. Later, therapists introduced thermal differentiation: application of cold, lukewarm, or hot water in accordance with the patient’s specific needs. By the first century BC, the Romans had developed hypocaust heating systems (the original central-heating principle) and were employing them in the heating of water for therapy. Roman thermal baths eventually featured highly sophisticated technical and therapeutic methods. The rooms of a medicinal Roman bath were configured in a ring, in accordance with a bath ritual. The sequence of rooms and treatments were as follows: undressing (apodyterium), hot-air exposure (sudationes), sweating (laconicum), hot bathing (kaldarium), temperate cooling-down (tepidarium), and cold bathing (frigidarium).