At 150 miles, Jewel Cave is the second longest cave in the world. It is filled with calcite crystals and other wonders that make up the "jewels" of Jewel Cave National Monument. Choose from a variety of cave tours for what's age appropriate for your kids. Reservations recommended.
This was the first cave my family ever visited, and it was a great experience! There were so many different things to explore, and it was well worth having to carry the youngest children through parts of it. Beautiful display of God's creation. We've visited other caves since then, but this remains my favorite!