The northern half of the city was designed into homocentric squares, which inherited traditions of the Han people. The northern and southern parts were separated by a river. Their major residents were Khitans and the Han people, respectively, and the two halves were governed by different systems.

"On the one hand, the Liao Dynasty emperors followed the principle to govern different people based on their customs," Dong says. "On the other hand, when building this city, they adopted feng shui and the idea of central dynasties of China to prioritize imperial power. It is thus a perfect example of a shared community comprising different ethnic groups."

In old narratives, the Liao Dynasty was often portrayed as having tense relations with the Northern Song Dynasty (960-1127), which ruled most parts of present-day Central, East and South China, but discoveries in Shangjing proved otherwise.

After Liao and Northern Song reached a truce in 1005, there was lasting peace between the two sides. Northern Song currencies found in Shangjing, for example, reflect their frequent trade exchanges. As Dong points out, the era marked a booming period of North-South cultural communication.

"Archaeological evidence has shown that the Khitan people inherited Tang Dynasty traditions in many ways, not only in terms of architecture," he says.

"Northern Song or Liao, if we take one side to see the other, our viewpoint will be biased. But if we put both in a bigger picture of China as a nation, our understanding of a united country with multiple ethnic groups will be greatly enriched," he adds.