This health resort 7km (41/2mi.) northwest of Keszthely, is one of the leading traditional Hungarian spa towns. Hévíz owes its international reputation to its thermal bath, the largest natural warm-water lake in Europe. As long ago as the late 18th C articles were already being written about its healing
properties, and in 1795 the first wooden bath-house was built.
The lake, which covers an area of 47,500sq.m (52,000sq.yd), is fed by radioactive water containing sulfur. The water comes from a spring lying 36m (120ft) down in a funnel-shaped trough and which pours between 60 and 80 million liters (13 and 18 million gal.) of water a day into the lake, thus completely changing the water every 28 hours. In summer it reaches a temperature of 33-34°C (91-93°F), and in winter never falls below 26°C (79°F), so the waters can be enjoyed even when it is quite cool outside. On the bed of the lake is a layer, several yards thick, of grayish-brown, coarse-grained mud which can be very effective in treatments involving the use of mud-packs. The pools in the spa hospital and hotels are also filled with water from the lake, and these establishments also provide additional medical treatment facilities. Those visitors who have come to Hévíz simply to enjoy the baths rather than for any specific medical reason are recommended to use the open-air baths at the northern end of the lake, where large numbers of water-lilies are in flower from April to October. The thermal bath and treatment facilities here lie in the midst of a nature reserve, surrounded by a beautiful park with lots of walks.