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Great Wall Of China

This is one of the beautiful wonders of the world and was built during the 7th century BC. It was later expanded by succeeding emperors to increase its length and height to tackle new threats posed by enemies from beyond the wall. The wall was built to protect the borders of the Chinese empire against attacks from nomadic tribes of the North and West and emperors were very successful in warding off attacks by arming the wall with troops and ingenious communication signals. It is the only man made wonder visible from space.