Under a flashlight the enigmatic beauty of the Fahai frescoes appears in its full glory. When the beam of light is thrown parallel to the frescoes (center), embossed parts of stucco and gold in the artwork are revealed.[Photo by Feng Yongbin/China Daily]

A closer inspection of the hole reveals a thread-like fiber structure. As thin as hair but much shorter, the material is mingled with mud and plaster to form the wall.

"In rural China it was common to mix straw and cornstalk with mud to build houses," Tao says. "The stalks acted as the bone of the wall, giving it support through what is known as its tensile strength. For the construction of the Fahai wall, mud was blended not with straw, but with goat's hair, which has much greater tensile strength. Egg white might also be added to provide adhesiveness to the mix."

The goat's hair and egg white may have reduced the wall's vulnerability in the hands of nature, but it needed a courageous soul to save the frescoes from those determined to have them destroyed.

The last time Ding Chuantao, 82, visited Fahai Temple was in 2010. But between 1966 and 1981 the Chinese language teacher at Beijing No. 9 Middle School lived in the temple grounds.