A highlight of their protection efforts is a project they carried out to protect the city wall, the result of which can be seen in an exhibition hall.

Cao says in a damp environment, soil can deteriorate, discolor, or become moldy.

Taking an intersecting surface unveiled in the archaeological excavation in 1992 for experiments, they explored how to protect it.

"In the 1990s, we tried ways of protecting the surface but could only preserve it for one or two months, and later it continued to deteriorate. In 2016, we wanted to explore if we can protect it with advanced technology," says Cao.

After multiple experiments, they managed to find a way of restoring the wall to its original state and keeping it intact in the long term. The technique won a national prize for protecting cultural relics in 2018 and has provided important reference for the protection of other artifacts.

"Now, the wall has highly similar texture and color compared with the time when newly unearthed, meaning it has been preserved very well," says Cao.

Archaeological progress continues on the Liyang Plain. Archaeologists are excavating the Jijiaocheng site and have found that it was probably an ancient state that rose when Chengtoushan was declining.

"Now, the studies of Jijiaocheng are at the starting point. Covering a stunning area of 10 sq km, it may need a new way for protection and promotion, and that's what we will consider in the next step," says Cao.