The City wall of Visby (Swedish: Visby ringmur) is an old medieval defensive wall surrounding the city. The building of ringwall was probably started in the 13th century. Around 1280 it was rebuilt to reach its current height, along with the addition of its characteristic towers (although some towers were not constructed until the 15th century) It is part of the UNESCO World Heritage Site in Visby. The war in 1288 between the citizens of Visby and the Danish army gave the citizens of Visby a reason to continue the work with the wall. All together the city wall became 3.4 km, and it was finished in the beginning of the 14th century. At the time, the wall contained 29 towers, 27 of which are remaining today.
During the 1361 Battle of Visby, the main battle was fought within 300 meters of the North Gate of Visby (shown on the right). The peasant forces were ultimately unsuccessful, however, resulting in the citizens of Visby surrendering to the Danish forces.
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.