Jewel Cave National Monument
Jewel Cave National Monument in Custer, SD contains Jewel Cave which is currently the third longest cave in the world. The cave has been mapped with 181.89 miles of passageways. In 1908, it became a national monument. Jewel Cave is Open year round and three tours are offered. The scenic tour loops a half mile through a paved and lighted cave portion accessible by elevator. A candlelight tour (a historic tour) will take you through the earliest discovered part of the cave. Lastly, there's a Wild Caving Tour where you can explore an undeveloped part of the cave located near the scenic loop.