The Anastasian Wall, also called the Long Walls of Thrace is a wall fortification built by the Eastern Roman Empire, to protect the city of Constantinople (Istanbul in present-day Turkey) from Barbarian invasion.
The accepted date for the collapse of the Western Roman Empire was approximately 476 CE, when the last true Roman Emperor Romulus was overthrown by Odoacer, the Germanic leader who became the first Barbarian to rule Rome.