From 2003 to 2004, archaeologists from the IACASS, the Shanxi Provincial Institute of Archaeology, and the Cultural Relics Bureau of Linfen Prefecture, unearthed a Middle Taosi period semi-round foundation – just beside southern wall of the Middle Taosi enclosure. It consists of an outer semi-ring-shaped path and a semi-round rammed- earth platform with a diameter of about 60 metres and an area of nearly 1700 sq m. The platform is 42m in diameter and over 1000 sq m in area. It can be reconstructed as a three-level altar. The outer first level is crescent in shape and 23 to 30 m to the centre of the altar. The second level in the middle is semi-ring in shape and 19 to 21 m from the centre. The third level or the top of the altar is semi-round in shape and around 13 m from the centre. An arch-shaped rammed earth foundation facing the east with 12 slots, each 0.15 to 0.2 m wide and 1.4 m between each other were discovered on the top of the altar.
Latitude: 36 09N Longitude: 111 27E
Certain features of the slots indicate that stone or wooden posts in rectangle or diamond shape might have been erected on the rammed earth foundation with slots between them. Standing in the centre of the altar and watching through the slots, one can find that most of slots respectively orientate to a given point of the Chongfen Mountain to the east. Therefore, a reasonable inference is that the slots might have been intentionally constructed in for astronomic observation of the sunrise on a particular point in a given day in order to establish the local solar calendar which is crucial for the practice of agriculture at that time. In other words, the altar is an observatory.
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, believes 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 40 metres in diameter, surrounded by 13 pillars which were are believed to have been used to mark the movement of the sun through the seasons.
The legendary Emperor Yao is said to have established his empire in this area 6000 years ago.
It "was not only used for observing astronomical phenomena but also for sacrificial rites. The ancient people observed the direction of sunrise through the gaps, and distinguished the different seasons of the year" - He Nu, a researcher at the Chinese Academy of Social Sciences.
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.
The Linfen River (Linfen he) is the second longest tributary of the Yellow River (Huang he).