St Michael's Isle, popularly referred to as Fort Island, is noted for its attractive ruins. There is evidence for human activity on the island from the Mesolithic period onwards and there are two ancient buildings on the island. Both are in a state of ruin and closed to the public, though there are a number of walks which allow visitors to explore the surroundings.
St Michael's Chapel, a 12th-century chapel, is on the south side of the island. This Celtic-Norse chapel was built on the site of an older Celtic keeill.
The island is the site of two great battles for the control of the Isle of Man in 1250 and 1275, when England, Scotland and the Manx were fighting for control of the island. The Manx won the first battle, but 25 years later they lost control to Scotland.
Derby Fort, a 17th-century fort, is at the eastern end of the island. It was built by James Stanley, the 7th Earl of Derby and Lord of Mann in 1645, during the English Civil War, to protect the then busy port of Derbyhaven.
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.