To protect themselves from raiding nomadic tribes, people in ancient China built walls around their homes, around their towns and around their country. There are so many walls in China that if they were added together they would circle the Earth twice. Take a virtual trip to China to check it out.
Video clip, from Secrets of the Great Wall (2000), broadcast by the Discovery Channel. Copyright, Discovery Communications, all rights reserved. Online, courtesy PutClub.com via YouTube. Clip provided here as fair use for educational purposes.