"This can leave them damp, allowing mold to grow and salt to form on the surface. As water leaks into cave temples, it puts these ancient pieces of art at risk," explains Wang, who has spent more than a decade restoring 1,300-year-old rock carvings in Chongqing's Dazu district.

As of last year, 13 heritage sites around the country related to cave temples or rock carvings had made it onto the UNESCO World Heritage List.

This includes the Mogao Grottoes in Gansu province, the Yungang Grottoes in Shanxi province, the Longmen Grottoes in Henan province, and the Dazu Rock Carvings in Chongqing.

Li Qun, director of the National Cultural Heritage Administration, says that Chinese cave temples display remarkable characteristics in terms of their subject matter, content and artistic style, which reflects the continuity, innovation, unity, inclusiveness and peaceful nature of Chinese civilization.