Wikipedia
Caumasee (Romansh: Lag la Cauma or Lai da Cauma) is a lake near Flims, in the Grisons, Switzerland. It is one of the lakes on the Flims Rockslide deposits. The lake is fed from underground sources. Its surface area is 10.3194 ha.
The level of the lake varies by approximately 4 to 5 meters along with the varying underground water flow during the year, hence reaches its minimum by the end of April when snow melting in the mountains increases. A maximum level is reached by mid July but may be topped in August even after previous falling due to summer rain. The very western bay never freezes in winter, probably showing a maximum water flow in this area.
When the lake is at a low level, with a small volume of water, it warms up sooner than most lakes in the region, so people can be seen starting to swim the lake in April while bigger lakes even in lower areas of Switzerland remain rather cool. Water temperature in summer is at an average 21 Celsius, with a maximum around 24 Celsius.
The lake is located in a huge Forest that was allowed to remain on the agriculturally useless debris area of the biggest prehistoric rockslide in the alps region and can only be reached by a footpath (wheelchair accessible), possibly using a funicular built in 1939, refurbished in 1988 on its original tracks (running May to October only). The walk from the edge of town to the funicular takes about 10 minutes.