Archaeologists in northern China have reportedly found one of the world's oldest observatories.
The remains, discovered near the city of Linfen in Shanxi province, are thought to be about 4,100 years old.
Wang Shouguan, a researcher at the Chinese Academy of Sciences, told state media that the discovery would help the study of ancient astronomy.
Chinese astronomers are thought to have made some of the earliest recorded observations of the stars.
The observatory consists of a semicircular platform 40m (130ft) in diameter, surrounded by 13 pillars which were are believed to have been used to mark the movement of the sun through the seasons.
It "was not only used for observing astronomical phenomena but also for sacrificial rites", He Nu, a researcher at the Chinese Academy of Social Sciences, told Xinhua news agency.
"The ancient people observed the direction of sunrise through the gaps, and distinguished the different seasons of the year," he said.
In order to test this theory, archaeologists reportedly spent 18 months simulating ancient uses of the site.
They found that the seasons they calculated were only one or two days different from the traditional Chinese calendar, which is still widely used today.