Jewel Cave National Monument - Visitor Center
Address: 11149 US Hwy 16, Bldg. B12, Custer, SD 57730
Jewel Cave, glittering with calcite crystals that gave it the name, is one of the longest caves on Earth, with more than 220 miles of mapped passages beneath the Black Hills, and explorers are still finding more. Theodore Roosevelt protected it in 1908.
Take the Scenic Tour past the sparkling crystals; young kids can earn a Junior Ranger badge. For a challenge, book the Wild Caving Tour, a half-day crawl through undeveloped passages with a headlamp.
Coordinates: 43.72985, -103.82950