Historical literature shows that during the Liao Dynasty there was a well, known as Yijing (Justice Well), near the excavation area, and next to it was a temple known as the Yijing Vihara. During the reign of Jin Dynasty Emperor Shizong (1161-89), the Vihara was used as a royal temple and renamed the Dajue Temple, and a palace in the temple was used to store royal archives and articles for sacrificial ceremonies.

Archaeological researchers infer that the earlier complex is related to the Yijing Vihara, and the later complex is related to the Dajue Temple.

"It's a very important discovery for the archaeological study of the Jin Dynasty," says Dong Xinlin, a researcher with the Institute of Archaeology, Chinese Academy of Social Sciences.

He says that Beijing was regarded as a secondary capital called Nanjing (Southern Capital) during the Liao Dynasty in 938, and regarded as the primary capital when it became Zhongdu under the Jin Dynasty. Since then, the Yuan, Ming (1368-1644) and Qing (1644-1911) dynasties all made the city their capital.

"Although we have a great deal of understanding of Beijing as the capital of the Yuan, Ming and Qing, we don't know much about it during the Liao Nanjing and Jin Zhongdu periods, and haven't found many artifacts from the periods. That's why this excavation is significant," says Dong.

"It implies that in today's districts of Xicheng and Fengtai, large-scale architectural sites from the Liao Nanjing and Jin Zhongdu periods may still be well-preserved, so we need to be careful to protect them from construction in the future," he adds.