Based on astonishing archaeological finds and extraordinary first-person accounts, this film tells the story of one of the greatest wonders the world has ever known: The Great Wall of China . The Wall is more than 3,000 miles long and was built in just 20 years by a workforce of nearly 50,000, who used technology and construction techniques that still inspire awe today. But this triumph of engineering came at a colossal cost and would eventually hasten the end of the Ming dynasty.