From Wikipedia: The Reed Flute Cave (Chinese: 芦笛岩; pinyin: Lúdí Yán) is a landmark and tourist attraction in Guilin, Guangxi, China. It is a natural limestone cave with multicolored lighting and has been one of Guilin’s most interesting attractions for over 1200 years. It is over 180 million years old. The cave got its name from the type of reed growing outside, which can be made into melodious flutes. Reed Flute Cave is filled with a large number of stalactites, stalagmites and rock formations in weird and wonderful shapes. Inside, there are more than 70 inscriptions written in ink, which can be dated back as far as 792 AD in the Tang Dynasty. These aged inscriptions tell us that it has been an attraction in Guilin since ancient times. It was rediscovered in the 1940s by a group of refugees fleeing the Japanese troops.
No photographer given. Found here.