Lake Hévíz is the biggest extensive medicinal lake in the world with 4,4 hectare water surface. The temperature of the water is 39,8 C in the spring cave, 34-36 C in summer and 26-29 C  in winter. The medicinal water of Lake Hévíz prush to the light from a dolomit stratum. Place of the spring had changed on several times. The springs prush to the light from a 18 m diameter spring cave. These springs have different temperature. The curative effect of the lake is due to the chemical composition of the water, the temperature, the slow movement of the water, the stirred plat and mud. The water output of the lake is 410 l/sec. The daily water output is 35 million litre. The water of the spring lake are changed during 3,5 days. The medicinal water in Hévíz contains sulphure, alkali-hidrogencarbonate andit is a bit radioactive. The water recommended for: bath cure, drink cure, joint pain, rheumatic illneses, locomotor disorders, gout, back-bone problems, Bechterew disease, gynaecological diseases, stomach illnesses.