Tvis Abbey is a former Cistercian abbey founded in 1163 by Prince Buris as a daughter house of Herrevad Abbey in Scania (now in Sweden). The abbey was dissolved during the Reformation, probably in 1547. The abbey church, which served as a parish church, was demolished, apparently in 1698, after which a replacement was set up in the west wing, but that too was demolished after the construction of a new parish church in 1887. Today there are no visible remains apart from the foundations.
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.