Maybe I'm wrong idk but they're all over Europe. Sometimes they're called adder.
Discussion
Now i saw that this is indeed what you say here https://en.m.wikipedia.org/wiki/Adder
The map includes just a very small part of Greece. So we have other species of vipers, that is why i confused. Here is one in a picture of mine, with a viper traped in a barel with water. Look the difference in the head (zoom it)
