Casteldoria Castle was built around the 12th century by the Genoese Doria family, and passed from the Genoese dominion to the Aragonese, then to the Arborea Giudicato and lastly to the Malaspina family.
Only a few ruins remain of the fortress: parts of the walls, the remains of a chapel and a large cistern that was probably used to collect and store water. The famous tower, on the other hand, is well-preserved, and is an important part of the castle, built in large, rectangular granite blocks set in mortar. Twenty metres high, it has a pentagonal layout with the entrance on the north-eastern side. On the same side are two large, non-aligned openings, and a large window on the opposite side on the first floor. Inside, the castle has three wooden floors with a tiled roof and walkway. The last floor was created from what was originally a mezzanine floor before a terrace.
References:The Walls of Constantinople are a series of defensive stone walls that have surrounded and protected the city of Constantinople (today Istanbul) since its founding as the new capital of the Roman Empire by Constantine the Great. With numerous additions and modifications during their history, they were the last great fortification system of antiquity, and one of the most complex and elaborate systems ever built. They were also the largest and strongest fortification in both the ancient and medieval world.
Initially built by Constantine the Great, the walls surrounded the new city on all sides, protecting it against attack from both sea and land. As the city grew, the famous double line of the Theodosian Walls was built in the 5th century. Although the other sections of the walls were less elaborate, they were, when well-manned, almost impregnable for any medieval besieger.