Great Wall of China is protected by a coat of lichen and moss.

The Great Wall of China is protected from erosion by a layer of moss, lichen, and cyanobacteria known as a "biocrust." This biocrust covers over two-thirds of a 600-kilometer section of the wall and helps to strengthen it, keep it dry, and protect it from wind and water erosion. The biocrust also acts as an insulator, reducing temperature extremes and the effects of salinity. These findings suggest that vegetation on ancient structures may play a crucial role in their preservation and stability. [Extracted from the article]