Trematon Castle was the caput of the feudal barony of Trematon. It overlooks Plymouth Sound and was built probably by Robert, Count of Mortain on the ruins of an earlier Roman fort: it is a motte-and-bailey castle and dates from soon after the Norman conquest.
Trematon Castle, like Restormel Castle, has a stone shell keep raised on an earlier motte. Although in ruins, much of the Norman walls remain standing, so that the original form of the Castle and keep are clear. The internal diameter is approximately 21 metres. A rectangular gatehouse, built in 1270, has two floors and a portcullis. Both are in good condition. The castle is currently open to the public.
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.