Pitsligo Castle originated as a 15th-century keep. There is an arched gateway in the west wall of the outer court, with the date 1656 and the arms of the Forbes and Erskines. In the inner court the date is shown as 1663. At the north-east angle of the courtyard there is a tall flanking drum-tower. The main tower had three vaulted stories, but almost all above the lowest has disappeared. There is a stair tower at the north-east corner which is better preserved. There are panels dated 1577 over the courtyard doorway.
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.