Fårösund is a decommissioned fortress, built from 1885 to 1886. Sweden's capacity to protect its neutrality was questioned after the Crimean War 1854–56. England and France persuaded Sweden to fortify the inlet at Fårö with artillery batteries and naval mines. The fortress consisted of three fixed batteries. At the turn of the century, the batteries were reconstructed. The batteries I and II were given modern quick-firing 57 mm guns, four per battery. In 1919 the fortress was closed down and all equipment removed. After the fortress was closed down and was taken over by the Swedish Prison and Probation Service in 1919, a penitential center was establishment. The fortress had been proposed as a detention center for social dangerous offenders, if and when legislation for such came about.
Today the fortress is a hotel and restaurant.
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.