The Bear Lake (in Romanian: Lacul Ursu): The heliothermal lake, created in 1875, is the largest heliothermal lake in the world.

Its shape resembles a spread bear skin, hence its name.

Its salt content is 100 g/l on the surface, 220-300 g/l deeper. Due to the heliothermic phenomenon, its water heats up to 35°C to a depth of 2 meters; but when the lake was formed, 80°C was measured in its warmest layer. Its temperature has decreased due to the incoming fresh water and bathers. The water of the lake has been used since the last century to cure infertility, but it is also recommended for the treatment of various rheumatic and inflammatory diseases.