The Gaocheng Astronomical Observatory, also known as the Dengfeng Observatory, is a significant historical site in Henan, China. Constructed in 1276 during the early Yuan dynasty, it was designed by the astronomers Guo Shoujing and Wang Xun. This observatory is part of the "Historic Monuments of Dengfeng in 'The Center of Heaven and Earth'" and was inscribed as a UNESCO World Heritage Site in 2010. It represents a long tradition of astronomical observations, from the Western Zhou dynasty to the Yuan dynasty, and includes a gnomon used for the Da Yan calendar in 729 AD.