Colossal Cave is a large cave system in southeastern Arizona, United States, near the community of Vail, about 22 miles southeast of Tucson. It contains about 3.5 miles of mapped passageways, and was discovered by Soloman Lick in 1879. Temperatures inside average 70 °F year-round. The cave is an ancient karst cave, classified as "dry" by guides. The meaning of this is that its formations are completely dry, or "dead", and do not grow.