In a beautiful setting with excellent views of the Mourne Mountains and Carlingford Lough, Greencastle is mainly 13th-century in date. It was built at royal expense and guarded the southern approach to the Anglo-Norman Earldom of Ulster.
After capturing the town of Carrickfergus in 1315/16, a Scottish army under Edward Bruce headed to the important town of Dundalk, one of the seats of Anglo-Norman power in Ireland. It was also a source of much-needed supplies. The Scottish force marched south, wreaking havoc on the Anglo-Norman Earldom of Ulster. It is likely that the settlements at Dundonald, Downpatrick and Dundrum were razed at this time, with Greencastle captured by the Scottish army of Edward Bruce and a garrison was placed in it under the command of Robert de Coulrath.
It was afterwards retaken by the Anglo-Normans.
Even after the ignominious end to the campaign in 1318, Edward’s brother Robert Bruce continued to maintain an interest in Ireland, even visiting the island on at least two occasions near the end of his life. It is known that in 1327 he visited Glendun on the east coast of County Antrim, and landed at Larne the following year. In 1328 he proposed holding a meeting at Greencastle in County Down to agree a peace treaty between the English and the Scots.
The castle continued to be used until the 1600s. It is now in state care. The most substantial part of the castle to survive is the rectangular keep. Only portions of the surrounding curtain wall remain. The ditch around the curtain wall was cut from rock.
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.