There is a cave in England that from the 1500s until 1880 was called "The Devil's A*se". It was renamed as Peak Cavern shortly before Queen Victoria visited for a concert.
Ajanta Caves in India are 29 caves joined together, which are filled with paintings from over 3 religions (Hinduism, Buddhism, and Jainism), which were constructed in 520 B.C. They cave system is spread over an area of 8,242 hectares, making it one of the largest man-made cave structures ever built.
The Vrtoglavica Cave in Slovenia has a 600-meter vertical drop, which is the longest such drop in the world.