The peninsula on which the Old Fortress has been built was uninhabited until 550 A.D. when occured the sack of Palaiopolis by the Goths of Totila. As a consequence, the city was gradually transferred to the naturally fortified and more secure nearby rock of the two peaks, the modern-day Old Fortress. This small rocky peninsula which extends eastwards into the sea would henceforth comprise the middle byzantine city called Koryphó. Much later, in the 16th century, the venetians constructed an artificial defensive canal, the so called "Contrafossa" which separated the peninsula from the island.
Below you can see an imaginative depiction of the peninsula made by Theofilos Tzikas before the byzantine Koryphó been built and a modern photo of how it looks like today from the same angle.