Dong visited the Shangjing site for the first time in 1998 and was fascinated by the possibilities it presented. In the years that followed, he covered every hill and knoll in the region, went to Yelyu Abaoji's mausoleum and where the Khitan leader's ancestors rested, and studied in detail the early history of the Liao Dynasty.

Many constructions were believed to have been destroyed during the war that ended the Liao regime. The Jurchen people, who established the Jin Dynasty (1115-1234), seized Shangjing in 1120 and massively altered the original structure of the city, which was then resided for a century before being abandoned.

Dong's persistence helped his team piece together the scattered and deeply buried puzzles, particularly after 2011, when large-scale excavation at the site was formally launched for the first time.

A decade of relentless fieldwork unveiled some of the city gates, which provided key clues to the evolution of this urban center. Ruins of the imperial enclosure, including palaces, were found, and so were many city streets. "We, thus, laid hands on rare physical materials to understand how the architecture developed," Dong says.

The Liao Dynasty was widely thought to inherit its style from the Tang Dynasty (618-907), a pinnacle of social prosperity during China's imperial period. From a mound in the west of the city, Dong's team unearthed a temple courtyard with three hexagonal pagoda foundations. Numerous exquisite earthen Buddhist statues were also uncovered.