Why don't you build a wall at the Ithmus of Corinth right over here? You might notice the geography of Greece. You have this little, I guess you could call it this little strip of land that connects the mainland, I guess you could say, to this peninsula, this very large peninsula, which is called Peloponnese, which is where Sparta is. And you could imagine that this is a very strategic location. Anyone who wants to conquer the Peloponnese by land is going to have to go through there. But the Athenians are, of course, no, we care about protecting ourselves. And so they start to build this wall to protect themselves, which the Spartans already are not so happy about.