'Stone doctors' help keep grottoes safe and sound

Carved into the cliffs along the Yihe River, the Longmen Grottoes in Luoyang, Henan province, stand as a UNESCO World Heritage site, encapsulating 1,500 years of Chinese civilization in stone.

While most visitors come to admire the site's graceful beauty, the "stone doctors" of Longmen see beyond the surface, identifying hidden threats like cracks and weathering that endanger these ancient treasures.

Ma Chaolong, deputy director of the center for grotto conservation research and heritage monitoring at the Longmen Grottoes Academy, is one of the "doctors" who has dedicated himself to diagnosing and addressing risks of the grottoes for 30 years.

He and his team employ advanced techniques like 3D scanning and environmental monitoring to detect even the slightest changes.

"All interventions follow one golden rule — minimum intervention," said Ma. "Preserving the old is also a way to move forward."

Tang Zhipeng, a 33-year-old staffer at the academy, used digital workflows to restore scattered Longmen statues.

"The academy has collaborated with many cultural and museum institutions across the country to explore a digital repatriation model," Tang said. By leveraging 3D digital technology, they achieved virtual restoration, allowing the pieces to be virtually restored, even though the real fragments could not be returned to their original position.

"So far, we have completed the digital restoration of over a dozen artifacts that used to be scattered, with their pieces lost overseas or housed in other cultural institutions within China," Tang said.

Li Xinjian, 51, a veteran conservator at the academy, said their conservation efforts draw on a cross-disciplinary team to tackle challenges like water seepage in the karst geology.

The cross-disciplinary experts include geologists, environmental scientists, chemists, biologists and mathematicians building AI-powered analyses.

The entire cultural relic protection industry is facing the problem of a shortage of professional and technical talent, Li said.

In the public's perception, the field of ancient heritage preservation is dominated by men. However, more than half of their frontline team are women born in the 1990s, who undertake high-intensity fieldwork on par with their male colleagues, Li said.

These female members are extremely sensitive while checking stones and keeping on-site records, Li added.

Li Peijun, a 35-year-old worker at the academy, said she often spent hours repairing broken stone statues and recording every detail of each artifact.

For her, every small fragment held a piece of history. "Repairing ancient stone was slow-paced and meticulous work. We must respect every mark left by time," she said.

Cui Donghao, 35, a Luoyangborn worker at the academy, said he has watched Longmen from different angles throughout his life. As a boy, he admired its beauty. In college, geology courses taught him to read the valley's rock layers and faults. In his work, the scenic monument became a series of research challenges. He assessed weak rock formations, rain-triggered harm and weathering risks.

Though technology has been increasingly applied, manual work still cannot be replaced, he said.

The newly found carving of The Diamond Sutra at Longmen Grottoes on the southern cliff illustrates the limitations of modern technology. This ancient text was uncovered not through automated scanning but by meticulous, hands-on inspection by workers. Once found, they created digital records to preserve the discovery.

"Heritage protection rarely yields flashy results. It demands consistent, daily effort," noted Cui.

At the 2026 Global Mayors Dialogue held in Luoyang this month, Yu Jie, Communist Party of China secretary of the academy, highlighted Luoyang's nationally pioneering preservation system, which mandates archaeological surveys before major construction projects to safeguard its rich cultural lineage.

"Looking at these stone carvings, I feel I am living through history. This is art, this is history, this is culture," remarked Roberto Di Stefano, mayor of Sesto San Giovanni, Italy.

While the outside world keeps racing past, the heritage guardians stay quietly beside the ancient cliffs day after day.

"Our heritage protectors respect ancient craftsmanship and feel responsible for preserving relics for future generations," said Zhang Zhimin, deputy director of the academy.

Wang Yuanting contributed to this story.