Moaning Cavern
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Moaning Cavern, California

Deep under the wooded hills of Calaveras County lies one of the state’s largest caves -- Moaning Cavern. There are two ways in -- the circular staircase or a 165-foot free-hanging rappel -- to a chamber big enough to hold the Statue of Liberty. (Stephen Osman / Los Angeles Times)
For the faint of heart, entree to Moaning Cavern is by stairs. Moaning Cavern earned its name from the sound created when dripping water echoes off the massive stone walls. The noise apparently lured dozens of prehistoric dwellers and curious Native Americans into the void and to their deaths. (Stephen Osman / Los Angeles Times)
A visitor pauses to admire the cavern’s rock formations from the 100-foot spiral staircase, which was built from old battleship parts in the 1920s. For regular folk, a 45-minute walking tour is available. For the wild at heart, there’s the three-hour adventure tour, which includes a rappel into the cavern. Now that’s a grand entrance. (Stephen Osman / Los Angeles Times)
For those rappelling into the main cavern, it’s just you, a rope and a lot of open space. Along the way down, the climber is likely to see “chocolate waterfalls.” The wet brown mounds, which look like melting chocolate balls clinging to the cave walls, are the product of dripping water laden with iron-ore deposits. (Stephen Osman / Los Angeles Times)
A suitably dressed visitor gets a feel for the cavern’s wall on the descent. Next up are squirms and shimmies through wet, rocky chutes. A diagram of Moaning Cavern resembles a crossword puzzle. Tunnels lead up, down and sideways. Don’t get lost. (Stephen Osman / Los Angeles Times)
The weird rock formations are the main reason to visit. Moaning Cavern and its maze of narrow tunnels was created over millions of years as acidic water eroded a monstrous slab of limestone under the green, pine-spotted hills of Calaveras County. (Stephen Osman / Los Angeles Times)
A visitor attempts to squeeze through the “pancake,” so named because it’s a rectangular gap, 3 feet wide by about 18 inches tall. Imagine the space under a Volkswagen Beetle. In the world of spelunking, this is what passes for fun. (Stephen Osman / Los Angeles Times)
Mid-tour, the spelunkers take a break in a small chamber. Each tight, twisting section of the subterranean tour has an all-too-appropriate name: First it’s the “meat grinder,” a passage that forced one visitor to twist his spine like a contortionist. Then the “guillotine” and, for added fun, the “roach motel,” “Godzilla’s nostril” and “Santa’s nightmare.” (Stephen Osman / Los Angeles Times)