Construction on the wall lasted through the 16th century B.C., and maintenance continues to this day.
The Great Wall is 6,400 km (4,000 miles) long and is the longest human-made structure in the world.
The people, soldiers and prisoners of China built the wall, not the rulers, and it is estimated up to 3 million Chinese died during the erection of the Great Wall.
It was difficult to transport outside materials, so builders used local resources such as stone in the mountains and compacted dirt in the areas lacking stone or other materials.
The most visited sections of the Great Wall are at Badaling, Simatai, Jinshangling and Mutianyu, all of which were built during the Ming Dynasty.
The Great Wall is one of the few human-made structures that are visible from space.
