World's highest lake:
Licancabur volcano contains the world's highest lake inside its 400 m wide summit crater at at 5913 m. The lake measures 90 x70 m and has a temperature of 6 deg C. Remarkably, the lake is located in the Atacama desert, the driest place on Earth, and has been present for at least the past 500 years.
The lake provides an extremely harsh environment, but still there is life (extremophiles, planktonic fauna): low-oxygen partial and atmospheric pressure and intense UV radiation. The lake is kept above freezing due to geothermal heating from vents in the crater. Licancabur lake has been compared to ancient Martian lakes.