My guess would be the Great Wall of China.
It is the great wall.
The Great Wall of China is the longest wall in the world, stretching over 13,000 miles. It was built to protect the northern borders of the Chinese Empire.
Northern China
The Great Wall of China is considered the longest man-made structure in the world, stretching over approximately 13,171 miles (21,196 kilometers). It was originally built to protect various Chinese dynasties from invasions by nomadic tribes.
The Gret Wall of China
the great wall of china
It became a world heritage site in 1987. It is the longest structure ever built and it is made all by hand. As well as it shows how China was ahead of their time when it was built. It also shows human interaction with nature.
the great wall of china
china
the Mongolia attacking china
Yes it is the longest wall ever you can even see it form space
To stop the northern invaders.