Korsholm Castle was a medieval castle in Vaasa. It was probably built in the 1370s and the oldest record dates back to 1384 (the testament of Bo Jonsson Grip, where the castle was called as Krytzeborg). The castle was originally built to a small island and it was surrounded by a moat and two walls. The castle itself was probably built of wood.
In the Middle Ages Korsholm was a property of several nobles. The most famous of them was Sten Sture the Older. In 1748 the new governor house was built to the site and all medieval structures were demolished. The next house was built in 1851 but it was destroyed by the great fire of Vaasa in 1852. Today a low mound is all that remains of the castle. There is also a monument dedicated to the castle.
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.