The 'Vauban Fortress' of Foras was initially a strategic fortification established by Philip the Fair, circa 1300. The donjon was rebuilt in 1480-1490 by Jehan II de Brosse.
The creation of the Rochefort Dockyard in 1666 made it a centrepiece of the system for defending the approaches of the Charente, which is prohibited from entering. At the end of the 17th century, François Ferry, the engineer of King Louis XIV, transformed the old feudal residence into the fort. In 1689, Ferry reinforced the walls of the Donjon to set up a battery of 9 canons and a signaling point. In 1693 a lower circular battery was set up to control access to the river Charente. The donjon received a signal station from 1889 to World War II.
Today classified as a Historical Monument, the castle houses a museum of regional history. Free entrance or guided tour of the fortification and the underground parts of the keep at 2 p.m every day (except Monday) between June 1st and the third weekend of September.
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.