People have used caves for shelter, tombs, and religious sites for thousands of years. Despite this familiarity, caves still hold a sense of mystery and danger. This survey dives deep beneath Earth's surface to explore how the world's largest caves formed, as well as what caves can teach us about Earth's past and the forces that are shaping our planet's future. Age-appropriate text with a strong STEM focus is supported by full-color photographs and a glossary of new or unfamiliar terms. Sidebars, fact boxes, and graphic organizers provide additional information on this fascinating topic.