We can see walls everywhere in the world. But the Great Wall of China is the biggest of all. The Chinese call it. "The Ten-thousand-Li. Great Wall." It's in fact   more than 6,000 kilometers long. It's 4-5 meters wide. In most places, five houses or ten men can walk side by side. When you visit the Great Wall, you can't help wondering   how the Chinese people were able to build   such a great wall thousands of years ago. Without any modern machine  , it was really very difficult to build it. They had to do all the work by hand. It took millions of men hundreds of years to build it. The Great Wall has a history of over two thousand years. The kings began to build the first parts of it around two thousand seven hundred years ago. Then, Qin Shihuang had all the walls joined up  . He thought that could keep the enemy   out of the country. Today the Great Wall has become a place of interest. Not only Chinese people but also people from all over the world come to visit it. The Great Wall was built   _  .
by people all over the world without any modern machines with some other countries' help by all Chinese Kings.