Aerial photo provided by the National Cultural Heritage Administration on Dec. 29, 2020 shows the excavation area of an ancient stone city site in north China's Inner Mongolia Autonomous Region.Photo:Xinhua

 
North China's Inner Mongolia Autonomous Region has uncovered prehistoric underpass ruins, said the region's institute of cultural relics and archaeology on Sunday.

Located in an ancient stone city site in today's Qingshuihe County, Inner Mongolia, the underpass was unearthed along with over 20 ruins, including city gates, city walls, building foundations, tombs, jade, pottery, and bone ware relics.

The stone city site, covering about 1.38 million square meters, belongs to the Longshan Culture, a late Neolithic civilization in the middle and lower reaches of the Yellow River.

The long and narrow passage is 5 to 6 meters underground, about 1 to 3 meters wide, and around 2 meters high, with an arched top. It connects the ancient city's inside and outside and its two trenches.

Traces of tool processing were found during the excavation, and its trampled surface was partly destroyed by fire, presenting vivid red colors.

The discoveries are of significant value to prehistoric cultural studies and origins of civilization in northern parts of China, said the researchers.