In the Middle Ages a chain suspended between two towers defended the entrance of Kyrenia’s little harbour, like the chain across the Golden Horn in Constantinople. William de Oldenburg, who visited Cyprus in 1211 during the reign of King Hugh I, referred to Kyrenia as “a small town well-fortified, which has a castle with walls and towers”. He perceived the chain tower as part of Kyrenia’s fortification system in that time. The Byzantines had already fortified the city, but in the thirteenth century, during the Longobard war, before the siege of the city, Frederick II’s party, under the direction of Captain Philippo Genardo, improved the defences of the city. The chain tower is still visible today in the north side of the old Kyrenia harbour. It consists of an 8,15 m diameter cylindrical tower and a 1,5 m diameter pillar on top of it. The tower was supporting a chain attached on the other side to another structure. The fortifications on the north side terminated against the harbour in a square tower or bastion holding the chain to be raised and lowered by means of a windlass. The paper includes the digital photogrammetric survey of the chain tower using a structure from motion software, the historical research and the comparison with other coeval harbour defence constructions of the eastern Mediterranean.