Lake Heviz is located nearby to the town of Heviz in Hungary, near the western end of Lake Balaton, approximately 8 kilometers away from Keszthely. The Lake Heviz has 47,500 square meters surface area; and it is Europe's largest thermal lake and the second largest thermal lake in the world. The Lake Heviz hot waters has different temperatures diffuse from fissures under the water’s surface, mix with the cold water of the lake to generate a continuous temperature that upholds throughout the season. The water is very rich in carbonic acid, calcium, sulphur, magnesium, hydrogen carbonate and even slightly radioactive substances that are well believed to have medicinal properties.
At the center of the lake is a wooden bath house constructed in the 18th century that looks more or less the same as it was more than two hundred years ago. Stunning water lilies, brought to Hungary at the end of the 19th century, dot the lake supporting the rich ecology. Mist covers the surface slowing down evaporation, and creepers protect the medicinal mud on the bottom of the lake. Lake Heviz-1 the peat-bottomed lake is mainly fed by cold and warm water rich in mineral content originating in springs located in a 40 m deep cave. The flow in the spring is so high that it is fully replenishes the lake every 3 days. The temperature of the Lake Heviz varies between 23-25 °C in winter and 33-36 °C in summer.
The lake’s curative effect is believed to be an effective product of the unique blend of organic and inorganic materials found in the waters. Therefore; Lake Heviz is a biologically active lake and home to a great number of bacteria. Certain of the species found in the waters is rare and unique to the lake. For example, Micromonospora heviziensis, bacteria that is a very potent protein and cellulose decomposer, can only be established here in the entire world. Likewise, for the two thermophile blue green alga species (Pseudanabaena papillaterminata and Pseudanabaena crassa), Lake Heviz is the only Hungarian habitat. Source: Charismatic Planet