Surrounded by snowy mountains, Lake Sils is the biggest lake in the Engadine Valley in the Swiss Alps. The lake surface of four square kilometres is currently covered with a 18cm of ice, and the frozen water creates strange noises that mystify and captivate those passing by. Because of temperature differences from above and below the ice layer, walking around and skating on the lake becomes a mystical experience. The cracking of the ice releases deep loud sounds which seem like they come from outer space.
Source: Swiss Info
