The Byzantine Castle of Thassos: The construction of the Byzantine castle at Thassos started during the Byzantine times. It was completed during Genoas Gattilusi's dynasty in the beginning of the 15th century. A narrow terracing atop the hill was a natural outcrop that juts into the sea and an important lookout post.
The castle was build as a fortress by Gattilusi, the Genoa dynasty that ruled over the island during the period 1414-1455. According to the inscriptions found in Agios Athanasios church, the first fortified settlement was made here in 1403 and the Gattilusi family remodeled the fortification during 1414-1416 to make it stronger.
Later the Turks occupied the castle and another inscription points to the fact that the castle was reconstructed by two residents of Constantinople named Constantinos and Ioannis. Till the end of the century, trade flourished and the settlement was an important commercial center even though not powerful enough to influence events.
The castle is ideally located at an altitude of 450m and erected on a rocky flat area that is inaccessible from most sides due to steep ravines and therefore well protected naturally.