The edible snail Helix aspersa, also known as Cantareus aspersus or as Cryptomphalus aspersus, has been spread all over the world by humans. Their land of origin may have been southern Europe. They have also been introduced to Turkey, perhaps by the Romans who liked to eat them, and are quite common in western Turkey in gardens, fields and ruins. Thanks to the unique patterns on their shells, they are among the easiest land snails to identify.
I found this young individual in Istanbul. I could tell that it hadn't completed its growth yet, because the edge of the aperture was quite soft. This soft area was marked off as a band ~3 mm wide (arrow in the photo). The veins covering the wall of the snail's lung were not visible thru this band, indicating that it was less translucent than the older portions of the shell. Either that or the lung didn't extend under the part of the shell that was still being built.
The last picture shows the snail's pneumostome, the breathing hole, thru which the lung opens to the outside.