Answer: Great Wall of China
Explanation:
The very famous Great Wall of China is a series of walls built from the 7th century BC to as recently as the 15th century AD.
These walls stretch way over 5,000 miles and are considered to be one of the greatest architectural feats of all time as troop barracks and watchtowers were included within the walls as well as it providing a means of warning about an invasion through signals.
