The Dalaborg Castle was built in 1304 by dukes Erik and Valdemar (the sons of Magnus Ladulås) during the war against the king Birger. The castle was destroyed in 1434 in the so-called Engelbrekt uprising. The Queen Margareta, regent of Norway and Denmark, was named also as a regent of Sweden in Dalaborg in 1388.
Today the moat, ramparts, a terrace and the cellar of a blockhouse remain of castle. A model of Dalaborg before it was destroyed can be seen at Mellerud Museum.
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.