<human>:  Why was the Great Wall of China built?
<bot>: The Great Wall of China was built to protect China from the Huns and other nomadic tribes. The Great Wall of China is a series of fortifications made of stone and earth, stretching across the northern border of China. The wall was built to protect China from the Huns and other nomadic tribes, and was completed in the 5th century CE. The Great Wall of China is the largest man-made structure in the world.