Archaeological site Dipylon in Municipality of Athens

You're standing at the Dipylon, the Double Gate. This was once the main gate of ancient Athens, and it's been called the largest gate of the ancient world. The whole complex was about fifty metres long and thirty metres wide. Take a look at the chunks of wall around you. Those are the cores of the towers that stood at each corner. Between the gates lay a square courtyard. Any attacker who got stuck in there was hit from every side.