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. (The National Cultural Heritage Administration/Handout via 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. /Credit Photo: BBC/

Area of the Longshan culture (3000–2000 BC) in northern China, based on Liu Li and Chen Xingcan (2012), The Archaeology of China: From the Late Paleolithic to the Early Bronze Age, 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. Cambridge University Press.