Crestasee (Romansh: Lag la Cresta) is a small lake shared by the municipalities of Flims and Trin in the Grisons, Switzerland.

From 1892 a guest house on its northern end served as pension and still is a restaurant today in its original state.

The rough character of the whole area derives from being a debris area of the gigantic Flims Rockslide, where waters flow underground until feeding lakes at certain spots such as Crestasee, Caumasee or Lag Prau Pulté.

In summer it is well known for swimming and offers facilities (such as a kiosk, toilets, changing room, boats and SUP's to rent[1]) to enjoy this.

A forest walk leads to Conn, to see the Ruinaulta gorge formed by the Rhine, still within the same huge rockslide debris area, or to the Lag la Cauma.