Dolbadarn Castle is a fortification built by the Welsh prince Llywelyn the Great during the early 13th century, at the base of the Llanberis Pass, in northern Wales. The castle was important both militarily and as a symbol of Llywelyn's power and authority. The castle features a large stone keep, which historian Richard Avent considers the finest surviving example of a Welsh round tower. In 1284 Dolbadarn was taken by Edward I, who removed some of its timbers to build his new castle at Caernarfon.
The remaining parts of the castle continued to be used as a manor house into the 14th century. By the 18th century, however, Dolbadarn Castle was ruined and uninhabited. From the 1760s onwards, however, it became a popular topic for painters interested in the then fashionable landscape styles of the Sublime and the Picturesque. J. M. W. Turner's 1800 work Dolbadarn Castle depicted the back-lit castle looming over the landscape and became particularly famous, but the paintings of the castle by Richard Wilson and Paul Sandby also represent important artistic works of the period.
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.