A «cave» is a natural underground space or hollow inside mountains, often formed when acidic water slowly dissolves certain rock, like «limestone», over thousands of years, leaving behind passages and wide chambers.
Inside some caves, beautiful rock formations called «stalactites» and «stalagmites» form. Stalactites hang from a cave's ceiling like fangs, because dripping water leaves behind thin mineral layers, while stalagmites grow upward from the cave floor the same way.
Special creatures that have adapted to permanent darkness live inside some caves, like bats, which use echolocation to move around instead of sight, and some blind fish that don't need eyes in total darkness.
