Clairvaux Abbey (Clara Vallis) was a Cistercian monastery in Ville-sous-la-Ferté, 15 kilometres from Bar-sur-Aube. The original building, founded in 1115 by Bernard of Clairvaux, is now in ruins; the bulk of the present structure dates from 1708. Clairvaux Abbey was a good example of the general layout of a Cistercian monastery.
From 1808 to 2023, the grounds were occupied by Clairvaux Prison, a high-security prison. As of 2024, it is in the process of being transferred to new ownership as a site oriented toward tourism.
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.