Eda Skans is a redoubt built by Gustaf Oxenstierna in 1657 against the threat of Denmark-Norway. It was rebuilt in 1676 and again in 1808. It was demolished when the union between Sweden and Norway was agreed. The restoration began in 1939 and today there isa museum where you can find an extensive collection of weapons, uniforms, paintings, documents and images. There are also findings from the lake Hugn here.
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.