And here a special one: The Kelefa Kastro, between Oitylo and Kelefa.

Thank You Johan,
We see, where and how these "castles" were built, one side on the cliff, so no easy approach, not really a castle but just a defensive wall, they would hide in there and defend as much as possible.
Such "castles" exist all around Greece, and along with the "communication" towers, who would pass the message at no time, for any incident, the population of the area would go in.
This specific one, is from 1670, built by the Turks.
Thank You Johan.