Secrets (2013)

Season 2: Episode 7

The Great Wall of China is more than just a part of history, it's part of the world's geography, a sprawling, massive edifice of mud, reeds, and billions of bricks. But why did the Chinese go to such lengths to build it? And what secrets have enabled it to survive for over 2,000 years? We unravel its mysteries and rewrite its complex history through groundbreaking science and pioneering drone technology. This is how the wall was built, what its real purpose was, how it has survived multiple earthquakes and attacks, and how long it really runs.