Solutional caves are formed by the dissolution of soluble rocks, such as limestone, by acidic water.

China is home to over 30,000 known caves, more than any other country in the world.

Krubera Cave in Georgia is the deepest cave in the world, with a depth of 2,197 meters (7,208 feet).

Carlsbad Caverns in New Mexico is famous for its extensive and well-preserved cave formations, including stalactites and stalagmites.

A chimney is a narrow, vertical passage in a cave that can only be climbed with the use of ropes or other climbing equipment.

The Puerto Princesa Subterranean River in the Philippines is famous for its navigable underground river, which flows through a cave system for over 8 kilometers (5 miles).

A hall is a large, open chamber in a cave, often with high ceilings and wide passages.

The Lascaux Caves in France are famous for their well-preserved cave paintings, which date back to the Upper Paleolithic era.

Erosion caves are formed by the erosion of soft rock, such as sandstone or shale, by water.

Jaskinia Niedźwiedzia in Poland is famous for its unique helictite formations, which are twisted and contorted cave formations.

Collapse caves are formed by the collapse of a sinkhole, which is a depression in the ground caused by the dissolution of soluble rock.

Mammoth Cave in Kentucky is the longest cave system in the world, with over 650 kilometers (400 miles) of explored passages.

Lava tubes are formed by the cooling and solidification of lava, creating a hollow tunnel.

Jeita Grotto in Lebanon is famous for its extensive underwater passages and chambers, which can be explored by boat.

Glacial caves are formed by the erosion of rock by glaciers, creating tunnels and chambers in the ice.