The largest land snail in the Istanbul area of Turkey, and in fact in many other parts of Turkey, is Helix lucorum. Despite the ongoing loss of wildlife habitats to incessant development in Istanbul, several species of native snails have so far survived in cemeteries, small parks and hillsides that are too steep for the construction of buildings. Helix lucorum is one of the survivors. The species is surprisingly common in certain parts of Istanbul. Many of them can be seen crawling in gardens and along walls after rainstorms.
Helix lucorum is edible and in the past, when there were more Greeks in Istanbul and elsewhere in Turkey who eat snails, while the Moslems usually refrain from doing so, the species was much exploited. The British explorer archaeologist Charles Fellows in the journal1 of his travels in Turkey during the years 1838-1842 wrote that "a brown shell-fish, in form similar to a large snail, and larger than a pigeon's egg" was much eaten in Çanakkale along the Dardanelles. Upon arriving in Istanbul a few days later, he corrected his diagnosis:
I have said that the people here eat a kind of shell-fish like a snail: I find it is a snail, and not a native of the sea, although sold by the fish-dealers. This morning I saw a dozen hampers of them; the well-known tender-horned inhabitants were gently peeping forth, but an occasional shake given to the hamper made them retire into their shells; the large brown kind I have before mentioned is the most common, but the people here also eat the more delicate small ones; as they are not considered meat, they add to the limited fare of the Catholics during the fasts. It is now Lent, and hence the greater display of them in the streets. The snail found in the chalk-pits near Epsom, and said to have been introduced into England nearly a century ago for medicinal purposes, appears to me of precisely the same species*.The snail Fellows saw was probably Helix lucorum.
It seems that the poor snails, once eaten and now kicked out of their habitats, will never get a break from humans.
Here is an old post about the epiphragm of Helix lucorum.
1Travels and Researches in Asia Minor. Available in Google Books.