"The Great Wall of China, also known as the Chinese Wall, is an ancient series of walls and fortifications located in northern China 12. It was built primarily to protect China from invasions and attacks from nomadic tribes in the north 2.

Construction of the Great Wall started as early as the 7th century BC and continued for several centuries under different emperors and dynasties 2. It is approximately 21,196 kilometers long, making it the longest wall in the world 25.

The wall is made of various materials such as stone, brick, tamped earth, wood, and other materials 12. Today, it is a UNESCO World Heritage site and attracts millions of tourists from around the world 15."