They say it's over 2000 years old, and more than 4,000 miles long. But even today nobody really knows for sure. The Great Wall of China is one of the world's famous buildings but it is still the least known. British writer and historian William Lindesay has lived in China for twenty years. Exploring the Great Wall has become his lifetime obsession.

• Gruppe 5
• National Geographic Channels International
• William Lindesay