Crestasee, Lake in Grisons, Switzerland

Crestasee (Romansh: Lag la Cresta) is a small lake at 844 m in the Grisons, Switzerland, shared by Flims and Trin. It lies in a hollow in the Flims Grosswald forest, fed by underground springs, with no surface tributary. Its outlet on the open northern side drains over a sill into the Flem. The water level varies little through the year.

The lake was first mentioned in a 1461 boundary charter between Flims and Trin, whose straight-line border between the lake, Conn and the Krummenwaag on the Rhine still holds. In 1828 a drainage tunnel failed; around 1870 Trin farmers emptied three quarters of the lake, but the calcareous sinter bed proved barren. Tourism began in 1892 with the guest house, renovated in 2001–2002.

The name Crestasee derives from Latin crista, meaning ridge, referring to the hill crest. The Romansh name is Lag la Cresta. Since 1892 the guesthouse at the northern end has served as a restaurant; it was renovated in 2001 and 2002. In summer a lifeguard supervises the lake and an entrance fee is charged.

The lake can be reached by car following signs toward Trin Mulin, or by public bus to the Felsbach Crestasee stop, from which it is about a 15-minute walk. The main season runs from May to September, when a kiosk on the northern shore is open and boat rentals are available.

The lake appeared in a Swiss Federal Railways poster showing a Canadian-style trapper with a dog overlooking the water, and in 2013 a Migros family picnic advertisement filmed here included a fire, which is forbidden at the lake; the long version even spliced in an intro shot of Caumasee.