The rock arch formation you're looking at today is Heaven's Gate Cave, a popular landmark in Hunan province, China. This busy tourist destination is located on Tianmen (Heaven's Gate) Mountain in Tianmen Mountain National Park. To reach the arch, you must either ride a cable car or take a bus up a twisty, winding road with 99 turns. (The number 9 represents eternity in Chinese numerology.) Once off the bus, you'll need to walk 999 steps up a 45-degree incline—a stairway to the heavens. It's no easy feat, but this is no ordinary cave. At an elevation of 4,100 feet, the arch is 440 feet high and 180 feet wide.