The Quoyness chambered cairn is located on Sanday in Orkney. It is approximately 5,000 years old and is located on the shoreside.
The cairn is about 4 metres high and can be accessed by crawling through the entrance passage, itself 9 metres long. Only half the entrance passage is roofed. A stone platform surrounds the cairn, and when originally built the cairn would have looked like Maeshowe today. Bones from 10 adults and 5 children were removed. The property is now in the care of Historic Scotland.
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.