The ruins of Xieqiqu. [Photo provided to China Daily]

She was a frequent visitor to the National Library, where she would leaf through its many archives dedicated to the Old Summer Palace, and found a gold mine of interesting material. In 2000 she proposed an archives project relating to the Old Summer Palace and planned to set up a database about the palace, starting with materials at the National Library.

Shortly before, the Beijing Municipal Administration of Cultural Heritage had started digging an archaeological site on the wasteland where the Old Summer Palace once was and invited Guo to formulate a study plan.

Guo then often rode a bicycle as she led students, among them He Yan, around the Old Summer Place searching for sites among the ubiquitous weeds. They painstakingly looked for and found the remnants of roads in the undergrowth leading to many sites that few people had reached, let alone seen. They found the steps of the palace of Shangxia Tianguang, the caves and artificial hills of Xinghua Chunguan, and the location of the island in the middle of the lake of Tianran Tuhua.

In 2006 Hengdian World Studios, China's largest TV and film production center, in Zhejiang province, built a replica of the Old Summer Palace, unleashing a public debate on whether China should rebuild the palace on its original site, and idea that found solid support.

But Guo insisted that "we should have a clear recognition of the nature of the Old Summer Palace. Currently, it is an archaeological park, a bearer and transmitter of historical information. If we replace that bearer with new buildings, we cannot see the original things".