Discovered by miners in 1851, this vertical chamber near Angels Camp is so massive it is the largest public cavern in California—big enough to hold the entire Statue of Liberty. Early visitors would climb into a large bucket and then be slowly lowered to the chamber’s floor. Nowadays, a spiral staircase provides easy access, or, if you prefer to get in touch with your inner Spiderman, consider rappelling the 165 feet/50 meters from the top of the chamber to the bottom. For intrepid explorers (prepare to belly crawl), a 2½-hour adventure tour delves into the cave’s deepest burrows, roughly 280 feet/85 meters below the floor of the main chamber, through narrow passageways with names like Meat Grinder, Pancake Squeeze, and Birth Canal.
If that hasn’t boosted your adrenaline enough, strap yourself in for a thrilling ride on a 1,500-foot/457-meter-long zip line. Check the website for a schedule of Concerts in the Cave, when the natural acoustics and sound of water dripping into the cave system (the so-called moaning that gives this site its name) is accompanied by live music and a light show or a singing choir.