Dun Borrafiach is an Iron Age broch located on the Waternish peninsula of Skye. It occupies a rocky outcrop overlooking the Borrafiach Burn. Dun Borrafiach has an external diameter of 16.5 metres, and the walls still stand to a height of 2.7 metres on the south side. The entrance is on the northwest side of the broch. The northeast side of the entrance-way appears to have been narrowed in antiquity by the insertion of additional walling. Inside the broch, a long stretch of the outer face of the intramural gallery is still visible on the east side.
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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.