Cullerlie stone circle, also known as the Standing Stones of Echt, consists of eight irregular stones of red granite arranged at approximately equal intervals to form a circle of 10.2 m diameter, enclosing the same number of small cairns.
At the time that the circle was built in the second millennium BC, the surrounding landscape was characterised by wet bogs, and the stones were transported to the site from higher ground some distance away. The tallest of the stones marks the north side of the circle. A 2004 survey of the site discovered that several of the stones had been carved with previously unnoticed cup marks.
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.