Restoration expert Cheng Yongmao speaks of his reverence for the original materials.

In order to ensure that the repaired sections reflect the original, the project is trying to minimize the use of modern materials. The bricks scattered around the site are picked up and reused.

"We will use every fragment of the original bricks, even a quarter of one, because some are over 400 years old," he says. "We have to honor the wall's legacy."

The demanding work requires physically fit workers, typically from mountainous regions like Chengde, Hebei province, who are accustomed to the terrain.