Hévíz has been known for its thermal lake, the largest in Europe, since the Stone Age. The Romans were the first ones to build baths in the area, and the modern-day Hévíz Thermal Bath was founded in the 18th century by the Festetics family who lived in Keszthely, five miles away. The Hévíz Thermal Bath complex sits on the lake, which never gets colder than 75 degrees Fahrenheit in the winter and can reach temperatures of 100 degrees Fahrenheit in summer, meaning it is a very popular tourist destination no matter the time of year; and many of the businesses in Hévíz cater to tourists who are in the town to enjoy the thermal lake.