Caumasee
Flims
this is a must-see in Graubünden. The color of the lake is breath-taking. Make sure you do not visit this place during summer as it will be super crowded any time of the day.
From Chur you can take the bus to Flims, Waldhaus and walk around 20min until you see the lake from above.
There is an automatic lift that takes you down. Note that it normally does not run during winter. The lake can get very crowded during summer but is also well visited in autumn due to the beautiful colors.
You can stroll around the lake and take some nice pictures.
If you like you can hike for around 1 hour through the forest until you get to the Crestasee (see my previous story). It is smaller and has not that teal color however it has a lot of charm and is less visited.