This castle was the stronghold of Western Christianity in the eastern Mediterranean for centuries. It was built by the Knights Hospitaller. After the crusades and their expulsion from Jerusalem the knights created a network of fortified ports and castles in Rhodes (1337-1522) and the other islands of the Dodecanese in order to control the passage of pilgrims traveling to and from the Holy Land. The imposing Nerantzia Castle is a typical example of a fortification of the 14th century. It was built at the eastern side of the town’s port that used to be a separate islet at that time and was connected with the main island via a bridge that exists to this day (the bridge at the Finikon Street). This castle safeguarded the town of Kos.
The medieval town of Kos that stretched from the archaeological site of the ancient port to that of the agora also had defensive walls at that time.
The well-preserved medieval fortress was built in three phases. Two of them took place during the period of the Knights’ rule and one during the period of the Ottoman rule. Firstly, the inner enceinte was built that is separated from the outer enceinte by a moat. It has four circular towers at its corners and the southeastern one has been integrated into the walls of the outer enceinte. The outer enceinte was built between 1495 and 1514. Its construction was considered imperative due to the technological transition from siege weapons (battering rams, catapults) to gunpowder weapons. It is clearly bigger than the inner enceinte with larger bastions at its four corners, battlements and cannon holes.
Both local materials and pieces that were taken from the ancient town (marble columns, inscriptions, architraves, column bases) were used to build the castle. There are many knights’ coats of arms on its superstructure. The circular tower at the left of the bridge connecting the two enceintes is worth checking out as it bears the coats of arms of two Grand Masters of the Knights Hospitaller, De Lastic and De Milly.