Why was the Great Wall of China built?

We all have heard the name of the Great Wall of China. this is the longest wall of the world, being more than 2694.4 kilometers (1684 miles) long. Its height ranges from 4.57 to 9.2 meters (15 to 30 feet)

while thickness is 9.75 meters (32 feet). The costruction of this great wall was started in the year 221 B.C. and it took almost 15 years to complete this work. This was built of stones and bricks. Now the question arises: what was the necessity of costructing such a huge wall?
This great wall was built to protect China from Mongol invaders. About the year 246 B.C. China was divided amongst small provinces. King Shih Huang Li united different provinces of China into an empire. To the north of this empire lived barbaric Mongols and theking felt that at any time they might attack his empire. To protect China from this danger he ordered the construction of a huge wall. So a wall starting from Shanhi Kuan in the bay of Pohai to Chiakuman in Kansuwas constructed.

Did the king achieve his goal? Unfortunately-no, because the wall was broken at many places and Mongols got an opportunity to attack China. The purpose of constructing the wasll ould never be fulfilled. Still many parts of the wall are broken. Now the Chinese have even taken to farming beyond the wall.