Moaning Cavern, Show cave in Calaveras County, California, US

Moaning Cavern is a show cave in Calaveras County, California, that leads visitors through a 165-foot limestone shaft into its main chamber. The system consists of winding passages and several smaller rooms with mineral deposits along the walls.

The cave was first described on December 7, 1851, in the Daily Alta California. Archaeologist Phil C. Orr later found human remains beneath mineral deposits estimated at about 12,000 years old. In 1922 owner Addison Carly leveled the cave floor for tourists, and commercial entry through an enlarged crack began in 1920.

The name comes from a moaning sound that echoed from the opening, which stopped once the entrance was enlarged for public access. The cave is an archaeological site: archaeologist Phil C. Orr found human remains beneath mineral deposits estimated at about 12,000 years old, and other bones are more recent. The Miwok did not bury their dead in caves, so how the remains arrived is unclear.

The temperature stays at 61 degrees Fahrenheit (16 degrees Celsius) year-round, so a light jacket helps even in summer. The descent follows fixed steps, and visitors should watch for wet surfaces and low ceiling sections.

The spiral staircase is 100 feet (30 m) high and was built in the early 1900s; the tour enters by a crack in the earth widened in 1920, while the original 45-foot chimney entrance is still visible at the start. Archaeologist Phil C. Orr found human remains beneath mineral deposits estimated at about 12,000 years old.