The early story of Beijing grows, as initial incarnations of the national capital gradually emerge from beneath the ground.

As it celebrates its 870th anniversary as the Chinese capital this year, archaeological researchers have stepped up efforts to clarify this history.

Large-scale foundations and precious cultural relics, such as jade books, porcelain, mirrors, pottery figures and building elements have been discovered at the Zhongdu (meaning "the central capital") site, which dates to the Jin Dynasty (1115-1234), the National Cultural Heritage Administration announced at a news conference in Beijing on Sept 28.

Zhongdu was mainly located in what are now the Xicheng and Fengtai districts. The current excavation in Xicheng district covers an area of 17,000 square meters, and was begun by the Beijing Institute of Archaeology in 2020.

The remnants of architectural complexes from two different periods have been discovered. The earlier complex dates back to the late Liao (916-1125) and the early Jin dynasties, while the later complex dates from the middle to late Jin Dynasty, possibly even the early Yuan Dynasty (1271-1368), according to Wang Jihong, the researcher at the Beijing Institute of Archaeology responsible for this dig.

The earlier complex, which has a seriously damaged base, was originally a courtyard enclosed by a winding corridor. The later site has a clear, complete layout, with two large symmetrical palaces in the north and south, and two symmetrical side rooms in the east and west.

According to Wang, the No 1 building base in the southern part of the later complex is a little smaller than the No 9 building base at the Taizicheng site in Zhangjiakou, Hebei province, and of a similar size to the palace of the shrine relics in Antu county, Jilin province, both of which have been identified as Jin royal architecture. This suggests that the No 1 base was also for royal use.

Highlighted artifacts unearthed from this site provide further proof. For example, archaeologists have found jade books recording the deaths of Jin royalty and an official's seal, showing that Jin-era Zhongdu was a political center for the dynasty, Wang says.

A large amount of high quality porcelain produced at famous kilns like the Jun Kiln, in what is now Yuzhou, Henan province, and the Ding Kiln, in what is now Baoding, Hebei province, has been unearthed. Some display features of the Southern Song Dynasty (1127-1279) and Goryeo Dynasty (918-1392) in Korea.

"The porcelain finds are evidence of the highly developed manufacturing of the Jin Dynasty and busy commercial activities in the city. They also prove that Jin Zhongdu was a commercial center, with its influence reaching neighboring areas," says Wang.

Articles of daily use and for entertainment, like chess pieces, inkstones, incense burners and combs, have also been found.

Established by the Jurchen people who overthrew the Liao Dynasty, the Jin Dynasty once occupied a vast swathe of what is today's northern China. They established a capital in Shangjing (Upper Capital) in present-day Harbin, Heilongjiang province, then moved it to Zhongdu in 1153.

Discoveries from the site illustrate the historical process that followed the move from Shangjing to Zhongdu. The large number of artifacts show the material achievements of the city at the time and vividly showcase the technological development level, art forms, and social life under the Jin Dynasty, Wang says.

"This provides plentiful evidence for the study of architectural craftsmanship, urban layout, handicraft development, and commercial trade during the Jin Dynasty," she adds.

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.