The Île Sainte-Marguerite island is most famous for its fortress prison (the Fort Royal), in which the so-called Man in the Iron Mask was held in the 17th century.
The island is first known to have been inhabited during Roman times, when it was known by the name Lero. In 1612, ownership of the island passed from the monks of Saint-Honorat to Claude de Lorraine, Duke of Chevreuse. Shortly after, construction of a fort on the island (to become the Fort Royal) began. In 1635, the island was captured by the Spanish and recaptured by the French two years later.
Towards the end of the 17th century, the Fort Royal became home to a barracks and state prison. During the 18th century, the present-day village of Sainte-Marguerite developed, thriving on the spending power of the soldiers stationed on the island.
The Fort Royal was home to a number of famous prisoners until its closure in the 20th century. As well as the Man in the Iron Mask, a mysterious prisoner whose identity remains unknown, Abd al-Qadir al-Jaza'iri (an Algerian rebel leader), Marquis Jouffroy d’Abbans (inventor of the steamboat) and Marshal Bazaine (the only successful escapee from the island) have all spent time there.
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.