The Great Wall of China, at 3,915 miles long, is the longest structure ever built by human beings. Construction of the wall began over 2,000 years ago. It was built in several different sections over many centuries by Chinese dynasties to protect against attacks and invasions from the north and as a border for military defense.
Nomadic tribes and bandits from what is now Mongolia and Manchuria often swooped down into Chinese territory to attack or rob. Early sections of the wall were made of stone, wood and mud, while workers during the Ming Dynasty in the 15th century B.C. used more durable stone and brick. It is said that over 1 million individuals died in its construction.
The highest point of the wall is about 26 feet, and the widest point is about 30 feet, wide enough for two cars to drive on. Sections of the Great Wall near Beijing are well maintained and are popular tourist attractions. Some older parts of the wall have deteriorated or been vandalized or destroyed to make way for other construction. A rumor that the Great Wall can be seen from space is untrue. As of 2014, attempts to capture a photo from space have failed.