San Cibrao de Las hill fort (Castro de San Cibrao de Las) is a hill fort of the so-called castro culture. Rather than a single castle, it encompasses an entire fortified town or village. The place was inhabited from the second century BC to the second century AD. It flourished during the first century, at the beginning of Roman rule in Galicia.
The ruins are located on a 473-metre-high hill, covering an area 384 m long and 314 m wide. Unlike the other hill forts of the area, there are many straight walls and fewer curving structures.
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.