Heviz is a spa town in Zala County, Hungary, about 8 kilometres from Keszthely. The town is located near Lake Heviz, the world’s second-largest thermal lake, but biologically the biggest active natural lake. Its temperature is affected by the combination of hot and cold spring waters, coming from 38 meters underground. The water breaks out from a spring cave, at approximately 410 liters per second, with a temperature of 40°C.