Gaocheng Astronomical Observatory, Astronomical observatory in Dengfeng, China

The Gaocheng Astronomical Observatory is a tapering grey-brick structure whose wide base narrows toward the top, divided by a vertical slot. Two rectangular chambers with arched windows and tiled roof ridges sit at the top, and stepped brick ramps slope up on the lower left and right sides. A long, low brick wall runs forward from the base along a paved walkway between grassy areas.

The observatory was established in 1276 under Emperor Shizu of the Yuan Dynasty as the central hub for 27 astronomical stations spread across China. This network allowed scholars to collect observations from multiple locations and coordinate their celestial research on a national scale.

The site is also called the Dengfeng Observatory, and the shrine of the Duke of Zhou stands here, where the Zhou Li places the centre of the Earth. South of the tower is a stone chart made by the Tang astronomer Yi Xing, and the two chambers on top once held a water clock and an armillary sphere.

The site is located near Mount Songshan and remains open to visitors under the care of the Dengfeng Bureau of Cultural Relics. Wearing comfortable shoes is recommended since reaching the observation platform requires climbing stairs and exploring the surroundings on foot.

Scholars working here calculated the solar year with only 26 minutes difference from modern measurements, accomplishing this about 300 years before the Gregorian calendar was adopted elsewhere. This precision shows how advanced celestial observation had become during this period.