Looking at scenery images, the Great Wall of China is well known quite long time. It is a series of fortifications being made of stone, brick, tamped earth, wood, and other materials. It was built along an east to west line across the historical northern borders of China in part to protect the Chinese Empire or its prototypical states. To do such thing, it wanna be against intrusions by various nomadic groups or military incursions by various warlike peoples or forces.
According to history of China, some walls were built in 7th century BC, and then the other joined together and created bigger and stronger walls. As seen presently, these are collectively referred to namely the Great Walls. More reading