Monolithos- Rhodes Island, Greece

Monolithos is one of the four strongest fortresses in Rhode. It is 237 meters hight and has a magnificent view to the sea. It was built around 1476 by the Great Magister D Aubusson on the top of the ruins of a Byzantine Castle. This fort remains impregnable.

For more information, refer this wiki page: http://goo.gl/HCSMR