China’s Tianmen Shan or the Heaven's Gate Mountain in Hunan province is named after an incredible cave natural arch eroded through the karst syncline. The Heaven’s Gate, as the arch is called, is located about 8 km south of the city of Zhangjiajie. It is accessed from Zhangjiajie by what may be the world's longest passenger cableway at a length of 7.5 km, followed by a bus ride along an 11-km long winding road with 99 bends called the “Heaven Linking Avenue”, that reaches the top of the mountain. From there a set of stairs with exactly 999 steps take visitors right underneath the 130-meters tall and 57-meters wide arch.
Tianmen Shan may be unique among the world's great arches in that its formation is recorded in history. Documents from China's "Three Kingdoms" period report that the entire opening formed in one cataclysmic event when the back of a huge cave collapsed in 263 AD. As a result, the name of the mountain was changed from Songliang Shan to Tianmen Shan. Thus, Tianmen Shan is also one of the very few natural arches with a precisely known age.
In modern times Tianmen Shan has become a target for stunt fliers. This is due to its location close to the Zhangjiajie airport as well as its large opening. Acrobatic flying teams have flown through the opening.