Carlow Castle has a large rectangular three-story limestone keep with circular towers at each angle. The castle dates from the early 13th century. It was built by William Marshal the elder in the time period between 1207 and 1213 which he spent in Ireland. The castle in Carlow was the very first of its kind in Ireland.
The castle was handed over to the crown in 1306, granted in 1312 to Thomas Plantagenet, confiscated by the crown in 1537 as the landlords were absent, bought by the Earl of Thomond in 1616, changed hands multiple times until it was taken by Oliver Cromwell in 1650 but was later returned to the Earl of Thomond. In 1814 the castle was widely destroyed in an attempt to create more space for the conversion into a lunatic asylum with the help of explosives. Just the outer face of the west wall and the two neighbouring towers could be preserved.
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.