"The flagstones used for paving the roads were unprocessed, adding rustic charm to the complex," Zhang says. "Records show it was built to imitate the Ming Dynasty (1368-1644) Tianyi Ge in Ningbo, Zhejiang province, which is one of the earliest surviving private libraries in the world. Based on the flagstones, it seems the Wenyuan Ge tried to reproduce the feel of the gardens of Jiangnan, the region south of the lower reaches of the Yangtze River."

Archaeologists found two ponds, one in the northeastern corner and the other to the south of the main hall, as well as supply and drainage channels linking them with a river outside the complex so that water was available to quickly extinguish fires. They also found that the courtyard was raised slightly higher than the surrounding land, so that surface water would drain outside through a wall drain when it rained heavily.

"Fire and water can both be devastating to books. As a result, people developed a refined system to mitigate the adverse consequences of both," Zhang says, adding that the complex's foundations are the most solid found so far in the excavation of the Yuanmingyuan.

The builders of the complex first dug a foundation trench, then laid wooden stakes on the bottom to prevent the buildings from sinking or shifting. On top of the stakes, they laid stone slabs, and on top of the slabs they built the building bases.

Zhang Lifang, an associate researcher at the Beijing Institute of Archaeology, says the foundations were so well made that they haven't subsided for hundreds of years.

"Although the complex was small in scale, they still made solid foundations," says Zhang Lifang. "This shows the stress on culture. The books the Wenyuan Ge once stored contained the essence of traditional Chinese culture. The care of these books across time has enabled Chinese culture to be passed down to the present day."

Of the four royal libraries in northern China, the Wenyuan Ge is the only one that no longer exists. Although it's unfortunate that the complex was destroyed, through archaeological efforts, details such as the flagstones used and the methods for laying foundations were discovered. "Through archaeology, sites can reveal more historical details," she says.

Ceramics, pottery vessels, as well as pottery and glazed building components have also been unearthed.

Archaeologists say the layout of the complex clearly conforms with sketches made in 1779 and 1898 by the Yangshi Lei — the architectural modeling standards of Lei's family, who presided over royal construction for the Qing Dynasty for generations — which means its layout probably remained unchanged after it became the Wenyuan Ge.