I was intrigued by the description of a small lake close to Bardonecchia (NW Italy), called “Green Lake” because it should look green, so I went there to check how much green it was… and it was a lot! The color is caused by a sort of green seaweed on the lake bottom. It is shallow, and the water is very clear, so the color of the seaweed is very, very evident, as you can see here. A wonderful walk in an enchanting valley.
Acid lake!