Greece is favored by a large number of thermal springs known since antiquity. It was believed that the springs possessed supernatural and healing properties and thus were also called healing springs. The Temple of Artemis in Lesvos island (NE Aegean Sea) is built over one of these springs. Hippocrates (460-375 BC), who is considered to be the founder of medical science and the “father” of hydrotherapy, extensively studied natural water and distinguished it into (i) stagnant, including water from mires and lakes, (ii) rainwater, and (iii) water rising through rocks, called mineral (metallic) water. He described the latter type as warm water containing sulfur, iron, copper, silver, gold, and other metals. The Roman physician Galen cured his patients by offering them off-season fruits, presumably cultivated in a primitive greenhouse heated by thermal waters.