Li Runde, former deputy director of the museum's department of architectural heritage, helped to identify the people in the photo and recounted anecdotes about the renovation process.

"It was winter. In order to protect the turret, we took it down temporarily and built a shed around it. Passersby all thought the Forbidden City had suffered an 'accident' and the turret was demolished. But we all knew that the foundation we laid makes it handy for future restoration," Li recalls.

The restorers have passed their torch on to the future generations of researchers and craftsmen at the museum ever since.

Xia Rongxiang worked at the museum from 1975 to 2017 as a carpenter, and participated in the restoration of two turrets in 1981 and 1985.

"The first 10 years after entering the museum were a golden time to learn the techniques," Xia says. By the second turret restoration project, he was the chief carpenter.

"I am greatly obliged to my two mentors, who told me that handling wood is like handling a tiger, that I could not fear it, nor back away," he says. "Despite the challenges I encountered, I never thought of flinching and could only carry on with the task."

Since retirement, Xia has been hosting courses for young practitioners at the Palace Museum and recently, for the exhibition, he was invited back to help curate the woodwork exhibits.

The Chinese title of the documentary literally means "I am at the Forbidden City for six centuries".