This is Karagöl, a lake located at 1330 m on a plateau in Sandras Mountain in southwestern Turkey. Karagöl means "black lake", although as you can see in the picture, when we were there on 9 July, it was neither black nor a lake. I had never been to that area before and I don't know anything about this lake other than what I observed during an hour or so we spent there. The "lake" is obviously a very shallow one and I suspect it dries almost completely in the summer.
The only freshwater snails we could find were under the numerous reddish rocks visible in the picture above. All the shells appeared empty.
They are planorbid snails (family Planorbidae). Lacking a microscope, we initially thought they were Planorbis planorbis, a species recorded from Turkey before. But P. planorbis is characterized by a keel around the periphery of the shell, which the specimens from Karagöl are lacking. A magnified photo of one Karagöl specimen is below. When I have a more definite identification, I will post it here.
Incidentally, these shells are almost completely flat and come very close to being planispiral.