Tianmen Stairs

At about 5,000 feet above sea level, Tianmen Cave is the highest naturally formed arch in the world — which has given the landmark its famous moniker. The impressive views and unique formation are the reason most people trek up the mountain. To reach the fantastic landmark, visitors must walk up 999 steps on the "stairway to heaven." Nine is a lucky number in Chinese numerology, representing good fortune and eternity. Those who wish to avoid the long cable car can opt to take a bus up a narrow roadway that bends back on itself 99 times. The cave itself is about 430 feet tall and 190 feet wide. It used to be a fairly ordinary cave until the year 263 A.D., when one side of the mountain's cliff collapsed and created the portal to heaven. Although be careful to whom you tell this origin story. Some believe that the cave's creation is a mystery, which only strengthens Tianmen's reputation as a holy mountain.