The l'île de Ré, opposite La Rochelle, was subjected on several occasions to attack from British soldiers. Conscious of the need to protect access to La Rochelle and Rochefort, in 1681 Vauban started strengthening the island's defences by building a citadel and fortified castle at Saint-Martin-de-Ré, on the North coast.
Built on the site of a fortress where construction work had started in 1627, the square-shaped citadel occupies the eastern part of the town. Its defensive system comprises four bastions, three demi-lunes and a counterguard, surrounded by a moat and a covered walkway. It contained an arsenal, food and powder stores, barracks and officers' accommodation. The citadel opens on to the sea via a small fortified port. From 1873 onwards it became a stop-off point for penal colony prisoners on the way to New Caledonia until 1897 and later to Guyana until 1938. Today it remains a prison for more than 400 detainees and is not open to the public.
An example of Vauban's first system adapted to suit a flat site, the construction was accompanied by an enormous fortified enclosure capable of accommodating the island's population of some 16,000 inhabitants, as well as their livestock, and of storing food supplies and forage in the event of enemy attack. In an arc on the land side, there are bastions, orilloned half- bastions and a counterguard. Two monumental gates, the Porte Toiras and the Porte des Campani form the access points. Also surrounded by a moat and a covered walkway, it is in addition encircled by an open-plan glacis, sloping outwards from the ramparts within canon-firing range.
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.