Hévíz, which is Hungarian for "healthy water," is located just 190 kilometres (118 miles) south-east of Vienna. Spa resorts are sprinkled all north of Lake Balaton, many founded in the 18th century. The oldest and most famous is five miles from Keszthely at Héviz, featuring Europe's largest thermal lake, the world's second largest. The first spa here was opened in 1795. With a temperature that rarely goes below 85-90 degrees, regardless of the season, Héviz has such voluminous springs feeding it that the entire lake replenishes itself every 24 hours. The therapeutic power of Lake Hévíz's minerals is so strong that it is recommended to limit your soaking to 20 minutes at a time. An enclosed causeway leads to the center of the lake where you'll find a palacsinta (crepe) bar, massage, float rental and other services. Stay at a deluxe spa hotel on the lake or in one of the many apartments or houses that may be rented.

There are several pieces of evidence proving that the thermal water of the Lake of Hévíz did not well up at the level in the geological past it does today but much higher. The water of the Hévíz Lake welled up at its present site about 20-22 thousand years ago, simultaneously with the formation of Lake Balaton. The warm water rushing up first flowed into Lake Balaton. Due to the changes in the climate the water level of Lake Balaton dropped. A peat-moor formed from the once lush flora in the former basin of the lake.