This lake is actually called "Morskie Oko", found in southern Poland right in the Carpatian Mountains, close to the tourist town called Zakopane, beautiful region.
Just like I said before, I was born close by and I miss it. I am inspired by these pictures and hope to set up some of mine on this website. Just a side note, it is not cold during the summer. And I am guessing that picture is made during the summer or spring. A little colder because of elevation, but short sleves are a must, after all that hiking! A great place to visit!