The Great Wall of China is one of the greatest wonders of the world. It rises up and down across deserts, grasslands, mountains and plateaus, stretching approximately 21,196 kilometers from east to west of China. The Great Wall is a series of fortifications made of stone, brick, tamped earth and wood, generally built along an east-to-west line across the historical northern borders of China. Originally conceived by Emperor Qin Shi Huang in the 3rd century B.C. to protect the Chinese states and empires against the raids and invasions of the barbarian nomads. It came to function more as a psychological barrier between Chinese civilization and the world, and remains a powerful symbol of the country’s enduring strength. Today, the Great Wall is generally recognized as one of the most impressive architectural feats in history.