Lake Hévíz among Rotatorias as well ("Epiphanes brachionus" var. "Spinosus", "Lecane inermis"), which are only present in warm waters. Jenő Ponyi has described the lake's primitive crustaceans in detail. Also a unique "Hydracarina acarus" is said to have found its habitat outside the fence surrounding the lake. The waters are reported to be beneficial to patients suffering from rheumatic diseases and locomotor disorders, among others. There is a thriving health tourism industry in the area. Lake Hévíz Lake Hévíz is located in Hévíz, Hungary, near the western end of Lake Balaton, from Keszthely. It is the largest thermal lake in the world,
Lake Ilopango Lake Ilopango Lake Ilopango is a crater lake which fills a scenic 8 by 11 km (72 km or 28 sq mi) volcanic caldera in central El Salvador, on the borders of the San Salvador, La Paz, and Cuscatlán departments. The caldera, which contains the second largest lake in the country and is immediately east of the capital city, San Salvador, has a scalloped to high rim. Any surplus drains via the Jiboa River to the Pacific Ocean. An eruption of the Ilopango volcano is considered a possible source for the extreme weather events of 535–536. The local military airbase,