Moaning Cavern

The Statue of Liberty would fit comfortably inside the depths of Moaning Cavern, one of California's largest caves, about 100 miles (161km) southeast of Sacramento in the town of Vallecito. From the opening to the cave floor, it's 165 feet (50m) down—a drop that seems to double if you're dangling from a rope above the abyss. Some visitors take the 234 scrap metal steps to the cave floor, but rappelling is a vastly more thrilling if terrifying way down.

The first half-dozen feet are easy, down a rock shelf, but then the bottom falls out, and nothing comes between you and the cave floor but your gear and thin air. The cavern is lit, so there's no mistaking the distance. As you and several others work your way down simultaneously, hand over hand, limestone formations come into view, as well as the stairs, one by one underscoring how far you are from solid ground. It's most nerve-wracking if a rappeller below you slows or stops or gets hung up; all you can do is hang there until he gets moving.

Once you reach the bottom, you're unharnessed and have the opportunity to learn about the cave. You'll see bones of prehistoric locals who lacked rappelling gear. The Miwok Indians reportedly used the cavern as a convenient burial ground years ago, and the bones of humans and animals have been found here. An optional 2-hour spelunking tour takes you through unlit, meandering caverns. You'll crawl or slide along the wet, muddy floors and squeeze through narrow openings to see some wonderful stalactites and stalagmites.

You'll need tied shoes to rappel down the sheer face—flip-flops don't make it. You'll also have to sign a release form and watch an instructional video before you start down. A member of the Sierra Nevada Recreation staff fits you with a hard hat, gloves, coveralls, kneepads, and lights. Then you move over to the "pit," where they check your gear, give you a few last words of instruction, strap you into your harness, and send you on your way.

Outside the cavern is a new 1,500-foot (450m) zipline, and horseback riding for an above-the-ground adventure. The nearby Calaveras Big Trees State Parkwww.parks.ca.gov) , with its Giant Sequoia trees, is worth a visit. So are the numerous old mining towns, small local museums, and additional caverns and mines. Golfing opportunities are available in nearby Angels Camp, which also has its share of antiques shops, galleries, and wineries.