The city of Syracuse, on the southeast coast of Sicily, managed to survive a protracted siege launched in 415 B.C. by Athens. To seal the city off, the Athenians began constructing a line of walls (shown in black) to enclose Syracuse, including a double wall, a wall leading north past a fort the Athenians used to guard their supply lines, and a wall (never completed) leading eastward to the sea. In defense, the Syracusans then put up several walls of their own (shown in green, red and blue) to prevent the Athenians from isolating the city.
In the end, these counter measures worked. When reinforcements from Syracuse’s ally Sparta arrived, the Syracusans were able to capture the Athenian fort. The siege of Syracuse then turned into an Athenian debacle, and many of the Athenian troops were slaughtered or imprisoned.