Lake Hévíz is located in Hévíz, Hungary, near the western end of Lake Balaton, 8 kilometres from Keszthely.
It is the largest thermal lake in the world which is available for swimming. The flow of water is very strong and the water in the lake is completely replenished every 72 hours. Its minimum depth is 2 meters, reaching a maximum depth of 38 meters, exactly at the point where the hot thermal water comes out to the surface.
Wikipedia https://en.wikipedia.org/wiki/Lake_Hévíz
Official Website http://www.heviz.hu/en/lake-heviz
Address 8380, Hungary
Coordinates 46°47'13.032" N 17°11'34.518" E