Picture of the Day: The Great(ly) Overgrown Wall of China

The Great Wall of China is a series of fortifications made of stone, brick, tamped earth, wood, and other materials. It was generally built along an east-to-west line across the historical northern borders of China. Several walls were being built as early as the 7th century BC. Since then, the Great Wall has been rebuilt, maintained, and enhanced; with the majority of the existing wall reconstructed during the Ming Dynasty (1368–1644).