The ancient working people are the designers of the Great Wall. They used different materials in different areas, for example, in mountains, they built the wall by bricks, and in desert, they used weed and sand.

The Great Wall is a complex structure, there are a lot to learn about this giant project, if you are interested in it, you can read more about it in this website, and probably, pay a visit to the wall, I think all your problems will be solved. :)