Colossal Cave, a dry karst cave in southeastern Arizona near Vail, has about 3.9 miles of mapped passageways and a much deeper human past than its tourist fame suggests. Between about 900 and 1450 AD, Hohokam, Sobaipuri, and Apache peoples used the cave. Its documented modern history begins with Mountain Springs Station in the late 19th century, followed by exploration, colorful local stories, and a brief guano-mining effort. The name Colossal Cave is usually tied to a 1917 survey made as tourism plans took shape. In 2025, guides added about 0.4 miles of passages and found water, suggesting parts of the cave may still respond to seasonal runoff.