Great Wall of China - Building Techniques

After China was united, the First Emperor sent 300,000 soldiers to the northern frontier to drive back invading nomads. When that job was finished, the army worked with 500,000 peasants to build the first part of the Great Wall.

This clip, from Secrets of the Great Wall (by Discovery Communications), demonstrates the techniques used to build the wall. It also shows how it was possible to build thousands of miles of wall within just twelve years.