Like the Rheinschlucht nearby, the Caumasee was also formed due to the largest known pre-historic landslide in the Alps. The lake itself (which is how See translates from German in this case) sits upon the debris deposited by the landslide.
The lake is located near the ski resort town of Flims in the Canton of Grisons in Switzerland. If you want a break from skiing, it is very easy to hike from Flims to the Caumasee, a perfect route for both beginners and veterans alike.
The walk from Flims to the lake and then around the lake should take no more than three hours at a leisurely pace. A great way to take a break from a long week of skiing!