The Karersee, or "Lago di Carezza" in Sudtirol. Even with throngs of tourists, it is a very spectacular place and well worth the visit.
Here you can see the Latemar mountain range in the background.
The colour of the water is amazing with various shades of green and turquoise. There is a viewing platform at the entrance to the lake, but you can also walk around the perimeter of the lake which I can highly recommend.
This photo is a panorama of three shots stitched together.