Dengfeng Observatory

(Local Name: Guanxingtai) Dengfeng Observatory, which is situated 14km/8.5mi from Dengfeng at the southeastern foot of Songshan, was built in 1276 and is the oldest observatory in China. The stone and tile building is 13m/43ft high and is equipped with a 31m/102ft long stone sundial.

This is where the famous astronomer and mathematician Guo Shoujing worked. In 1199, after many long observations and exact calculations, he was able to prove how long the earth takes to orbit the sun and was in fact only out by a mere 26 seconds.