1. Caves are giant holes in the earth that run horizontally underground. Vertical holes in the earth are called potholes.
2. The most spectacular caves, found in limestone, are called caverns. Acid rain trickles through cracks in the rock and wears away cavities.
3. The largest single cave is called Sarawak Chamber found in Malaysia.
4. The deepest cave gallery, at a depth of 800 metres, is found in the French Pyrenees.
5. The longest cave is Mammoth Cave in Kentucky, U.S.A.
6. Stalactites are icicle-like speleotherms that hang from the ceiling of the cave (the largest on record is 6.2 metres long). Stalagmites are icicle-like formations that poke up from the ceiling floor.
7. Caves often reveal the history of the local primitive people and prehistoric creatures.
8. Europeans sometimes use caves to age cheese or wine. The Italian word for cave is "grotto".
9. Glacier caves form due to the movement and melting of ice. Sea caves form when waves hit the weak parts of a sea cliff. Lava tubes form after volcanic activity.
10. Species that live in caves are called troglobites. They include: olms (dragon like amphibians), pseudoscorpions, wolf-spiders, cave snails and cave beetles.
Photo of Yellow Dragon Cave courtesy crunchpost.com.