In 1974, Guo, then 37, started his new career alone on Mount Beishan, one of the five most representative locations of the rock carvings.

He lived in a shabby cottage in the middle of nowhere, with no running water or electricity. His job was simple－safeguarding the grottoes and taking notes about their conditions.

"I never thought about giving up, although the living and working conditions then were really challenging," Guo says. "I really love those rock carvings and enjoy being around them."

Dazu Rock Carvings were listed as a major cultural site under the national protection in the 1960s, but not until 1980 did the National Cultural Heritage Administration begin to build complete archives for the national treasures.

Local bureaus must provide the introduction and images of the cultural relics. With no camera or surveying and mapping instruments, Guo decided to draw the grottoes himself.