Moon Hill is a hill with a natural arch through it a few kilometers outside Yangshuo. It is so named for a wide, semicircular hole through the hill, all that remains of what was once a limestone cave formed in the phreatic zone. Like most formations in the region, it is karst. It is also a popular tourist attraction. Moon hill offers some broad, panoramic views of the surrounding countryside, which is characterized by the knobby karst hills found throughout the region. (Wikipedia)