Château de Saint-Malo was built between 1424 and 1690, first by Jean V, the Duke of Brittany. The Duke Francois II built the first tower in 1475. In 1590 during the Wars of Religion the castle was occupied by local people, who wanted to prevent local governor to gave the city to Protestant king Henry IV.
The château was modified in the 17th century according the design of famous fortress architect Sebastian Vauban. In the 19th century it functioned as barracks. Today it is a museum, covering a number of themes including the long maritime history of St-Malo, 19th century writers of which Chateaubriand is the most well known, WWII occupation and the destruction and reconstruction of the town.
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.