This place does exist and it's called Munychia or Castella. It all starts after the end of the Great Peloponnesian War though, when Spartan leader Lysander formed an oligarchic government in Athens.
His Council of Thirty soon began suppressing its opponents. Which ultimately led Thrasybulus carry out an attack in the battle of Phyle which changed completely the course of things.
As soon as Thrasybulus felt he has the edge in the battleground -and with the crucial support of more than 1.000 warriors, he decided it would be worth trying to capture Piraeus, the port of Athens.
What's interesting about this is that Piraeus had always been a decree of democratic support.
The Thirty had even exiled some of their opponents from Athens in the port while in the previous years the Spartans had decided not to protect the city declaring the walls of Piraeus should even be demolished, so the town was now unfortified; an easy target to hit.
According to some accounts the Democrats captured the port at night, without any serious fighting. According to some others, the fight was long; its turning point being the killing of Critias, the leader of the Thirty.
The Athenians allegedly ended up basically occupying a crucial defensive position on the hill of Munychia, then an uninhabited hill to the north-east of Piraeus. The Thirty of Lysander attacked this position and were defeated.
After this defeat, the Thirty Tyrants were forced to flee to Eleusis and a governing board of ten was elected in their place; this new government, though, was not ready to compromise with the winners of Piraeus, so extra help was requested by Sparta. This paved the way for the battle of Piraeus and the final restoration of Democracy in Athens.
Cover Photo Credits: https://www.flickr.com/photos/freeblue/3357605998/in/photolist-67GBhA