The lake was created due to a prehistoric landslide down Mount Meßnerin, which now holds back the accumulating water. As the snow melts, the lake fills with water, and it can reach a depth of up to eleven meters. Meadows, benches, hiking trails and jetties are all submerged in the gleaming emerald green lake, but can still be seen and recognized under water. They reemerge as the water level drops in autumn. Swimming in the Grüner See is prohibited to prevent the lake bed from being stirred up and so that the green colour is retained.
