The Abbey of Saint-Gildas is dedicated to St. Gildas (c. 500–570) who was a British historian and cleric. He is one of the best-documented figures of the Christian church in the British Isles during this period. According a legend Gildas established the abbey, but there are no written evidences. Buildings were destroyed by Norman raids in the 10th century.
The first known record dates from 1008 when the abbey was restored by the order of Geoffrey I of Bretagne. The new inauguration was held in 1032. The heyday of Saint-Gildas Abbey was in the 11th-14th centuries. During the Hundred Years' War most of the archives were destroyed. The monastery started to decay in the 16th century. The nave of the church collapsed in 1668 when a lightning hit it.
the next restoration took place in the late 1600s. The abbey church was moved as a parish church during the Great Revolution in 1796.
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.