Mount Rushmore National Memorial is carved in the granite core of the Black Hills. There are no caves in the Memorial, however there is a ring of limestone around the Black Hills. This limestone layer was laid down at the bottom of an inland arm of the sea that covered the area around the Black Hills spreading east during the Cretaceous Era, 65 million years ago. In this limestone ring there are several caves, two of which are National Park Service sites, Wind Cave National Park and Jewel Cave National Monument. Check their websites for additional details on how the caves were formed and what their special features are.

Badlands National Park is approximately 1.5 hours from Mount Rushmore. Take I-90 east towards Wall, SD, to exit 110 or 131 to access Hwy 240's Badlands Loop Road. Check their website for additional information.

While visiting the Badlands you might also want to visit the Minuteman Missile National Historic Site. Visitors can get an upclose look at an intercontinental ballistic missile and be guided through the underground launch control facility. Check their website for additional information. 

If you are heading west from Mount Rushmore approximately 2.5 hours away is Devils Tower National Monument. travel west on I-90, exit at Sundance, WY, take Hwy 14 north to Hwy 24 and then take 24 north to Devils Tower. Check their website for additional information.