Maguelone Cathedral stands on an isthmus between the Étang de l'Arnel lake and the Mediterranean Sea in the Gulf of Lion, which was once the site of the original city of Maguelone, opposite the present-day town of Villeneuve-lès-Maguelone.
Maguelone Cathedral was once the episcopal seat of the former Bishop of Maguelone until 1563, when the see was transferred to the newly created Bishopric of Montpellier. The cathedral, constructed when the see was returned here in the 11th century from Substantion by Bishop Arnaud (1030-1060), is a Romanesque fortified building. Although parts, such as the towers, have been demolished, the main body of the building remains functional and is a registered national monument.
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.