For over 700 years Örebro Castle has kept a watchful eye on everyone crossing the bridge on the River Svartån. The oldest part of the castle, a defence tower, was erected in the latter half of the 13th century. This tower was added to in the 14th century to make a larger stronghold. The castle was expanded during the reign of the royal family Vasa between 1573-1627 to the impressive Renaissance castle.
After Vasa family Örebro castle was left to decay, but the main restoration took place in 1758-1764 by Carl Johan Crondstedt. After him the castle was used as a residence of county governor. The castle was finally restored to the 16th century appearance between 1897-1900.
Today there are guided tours, an exhibition centre and the castle is a very worthwhile sightseeing destination.
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.