Jewel Cave National Monument

It's the third biggest cave on Earth and we still don't know how deep it goes.

Think of all the spectacular places you have visited here in South Dakota. The summer vacations you've taken with your family as a child and maybe continue as an adult now with your kids.

One place that doesn't get mentioned nearly enough is this 'hidden gem' in the western part of the state. And most don't know that it's actually the third-largest cave on planet earth.

Of all the wonders of the great state of South Dakota, there are eight that stand out.