The fortress towering over the little Cretan town of Rethymno is a strange place. Built by the Venetians at the end of the 16th century to protect the town and its inhabitants from Ottoman invaders, it proved ineffective for this purpose in 1646, when it was taken after a short siege. The Ottomans demolished the church and built a mosque in its place.
When the Germans invaded Crete in 1941, the Fortezza was subject to air strikes before paratroops landed south of Rethymno. The Germans then used it as baracks and prison.
So the Fortezza is not really good for a symbol of Greek national pride, yet too prominent to ignore. Maybe it is therefore fitting that the cannon on the site are not mounted and in the positions the fortress has for them. I am actually not sure if these cannon were ever meant to arm the fortress. They could also be salvaged from the sea by the level of decay. But the climate on the Fortezza is very salty, with predominant wind from the sea and high waves, so they possibly have corroded away like this on land.