The fortifications of the Cittadella consist of a semi-circular enceinte in the northern end of the city, and bastions linked together with curtain walls in the south. The northern walls are built on the perimeter of the natural plateau, so they were difficult to attack. They were originally built in the 15th century, although large portions of the walls were rebuilt by the Hospitallers or in modern times. The northern walls include the remains of a collapsed medieval wall tower, a blocked-up sally port, a lookout post and some walled-up windows. Masonry revetments are built in depressions within the cliff face below the northern walls.