Beneath the southern Black Hills lies a labyrinth famous for a rare, delicate calcite formation. South Dakota wears its history on the land itself, and this landmark is a case in point.

Wind Cave holds one of the world's largest concentrations of boxwork, a honeycomb calcite feature.

What sets it apart

More than 150 miles of passages have been mapped, ranking it among the longest caves on Earth. That detail is easy to overlook, but it helps explain the pull this place has on locals and visitors alike.

The surface above protects one of the country's few remaining mixed-grass prairie ecosystems.

Why it matters

What ties it all together is a distinctly South Dakota balance between the wild and the worked-over. However you come to it, this is a place that stays with you long after the drive home.