Fredericia was established as a fortress town in 1650. On the land side, the town was laid out in circular form with nine large moated bastions. On the waterfront, the town had a somewhat weaker fortification line together with a citadel as its last defence. There is every indication that Fredericia was planned as a fortress town. The streets are regular and entirely perpendicular. Fredericia was the only town in Denmark with freedom of religion and right of asylum. In 1657, the fortifications were conquered by Swedish troops, and again during the Schleswig Wars I and II of 1849 and 1864. The fortifications were dismantled in 1909 and the green ramparts converted into a large public park.
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.