Archaeologists find 4,000-year-old sentry post in Shaanxi

After five years of excavation, archaeologists found the country’s largest prehistorical city site - Shimao Site in Shaanxi. There is a tall building on the stone wall of the site, which looks like a beacon tower on the Great Wall. The archaeologists speculate that it was a sentry post from 4,000 years ago. (Photo/Weibo)