Most visitors to the Acropolis leave with the impression that there was never anything on top of the rock, except impressive temples of white marble.
Nothing could be more misleading.
For most of its long history (and prehistory) the Acropolis was a fortress, walled against threats that remained real for hundreds of years, only to be replaced by others.
This broken cannon, apparently abandoned as useless, is just one of the several reminders that war (or the threat of one) was very much a fact of life here until quite recently.
Right next to the Parthenon, it doesn’t even register in the attention of the thousands of visitors that go by. And yet it is, as much as the Parthenon, a part of this place’s long history.