The Great Wall of China is an ancient Chinese fortification built and rebuilt between the 5th century BC and the 16th century (Modern Age) to protect the northern border of the Chinese Empire of the attacks of nomadic xiongnu of Mongolia and Manchuria.
Counting its ramifications and secondary constructions, it is estimated to be about 21,200 kilometers long, from the border with Korea, on the edge of the Yalu River, to the Gobi Desert, along an arch that roughly delineates the South border of Inner Mongolia, although today only 30% of it is conserved. On average, it measures 6 to 7 meters high and 4 to 5 meters wide.
The wall was designated a World Heritage Site by UNESCO in 1987.
