The Great Wall of China

The Great Wall of China is the longest structure built by the humans. It was even said to be seen from the moon, but only with the help of a telescope.
Great Wall of China is not just a long wall. It's a series of construction spread over the northern part of China, leaving the mountains and rivers on its way. It consists of watch towers, barracks and pathways.
The kingdoms in China built various walls during the 7th century BC to protect themselves from the invaders from the north. Later most of those walls were joined together by the Emperor called Qin Shi Huang who was the founder of the Qin dynasty in China.
Qin Shi Huang was considered as the first emperor of the China who conquered many tiny kingdoms and made it a huge empire. Huang (BC 206-221) built huge walls to defend his empire from his enemies called HUNS! Later the dynasties that succeeded the Qin dynasty also extended the wall.
Then came the Ming Dynasty, which ruled china from 1368 - 1644 AD. It often faced threats from the Mongols and other nomadic tribes. So the rulers of Ming thought of strengthening the Great Wall of China. It used bricks to build a better wall. Previously much of the wall was constructed with the help of rocks, sand and even flour. The Kings of Ming even added 25000 watch towers to find out the movement of the enemies.
After the fall of Ming dynasty, the extension of Great Wall has come to a halt. Some part of the Great Wall was destroyed due to natural disasters; a few more bits were torn down by people for using in their homes.
With a thorough study on the Great Wall of China spread over 15 provinces in China, the government of China through revealed its length to be 21,196 kilometers with an average height of almost 20 feet!
Though the government of China has taken steps for the restoration and preservation of the Great Wall, experts warn that almost 70 percent of the Great Wall is weak and ready to be destroyed!