Jewel Cave National Monument contains Jewel Cave, currently the second longest cave in the World, with just over 157 miles (253 kilometers) of mapped passageways.It is located approximately 13 mi (21 km) west of the town of Custer in South Dakota's Black Hills. It became a national monument in 1908.
Jewel Cave is open year round. The Park Service offers three tours: the scenic tour, a half-mile loop through a paved and lighted central portion of the cave accessible by elevator; the historic tour, a candlelight tour through the earliest-discovered part of the cave; and a spelunking tour, through an undeveloped part of the cave near the scenic loop. There are some surface trails. While reservations are not required, they are recommended during the summer seasons