Can anyone tell me some interesting facts about the Great Wall of China?

Well, I just know these. Hope they would be helpful. It was first built in Zhou Dynasty (1046BC-256BC) and last built in Ming Dynasty (1368-1644). It is among one of the eight wonders in the world. The wall we talking about nowadays actually refer to the Wall that built in Ming Dynasty. Its total length is about 5500 miles (8851.8 kilometers) The average height of the wall is 8.53 yards (7.8 meters), and average width is 7.10 yards (5.8 meters).

No It was first built in the Qin Dynasty.

No all wrong. A small section of it was started during the warring states period ( before China was one country ). Then the Qin dynasty worked on it.

it is more than 2300 years old it was built to defend off invasions from northern invaders.