Vaxholm Castle was originally constructed by Gustav Vasa in 1544 to defend Stockholm against shipborne attacks from the east, but most of the current structure dates from 1833-1863. The stretch of water below the building was formerly the main sea route to Stockholm. Thus, the fortress was strategically situated to defend the city from naval attacks. The castle was attacked by the Danes in 1612 and the Russian navy in 1719. Since the mid 19th century, its military importance has ceased. Today, it is home to the Swedish National Museum of Coastal Defence.
In 1970, it was used as a movie location for the pirate stronghold in Pippi Longstocking in Taka Tuka land. A scenic view of the castle may be seen from the car ferry which plies the short distance between Vaxholm and Rindö.
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.