Once an ancient sea, this landscape of rocky ravines is filled with the fossils of ancient marine life.

A diverse, expansive nature preserve in northeastern Kansas.

Curious rock formations in a tiny Kansas state park.

One of the Eight Wonders of Kansas and the first official National Natural Monument these stark formations look like nature's Stonehenge.

A wonderland of caves in eastern Iowa.

An underground wonderland in Iowa.

This tiny site in Iowa, part of a patchwork national wildlife refuge, is home to ancient flora and fauna.

The oldest university museum west of the Mississippi retains its 19th century feel.

Chilly air billows out from the entrance of an abandoned mine on a steep hillside, providing a refuge for Ice Age fauna and flora.

In the Shawnee National Forest, amazing rock formations peer through the treeline.

Once one of the world's great cities, Cahokia was a place of religious worship, trade and mass human sacrifice before being mysteriously abandoned.

Shop of curiosities with a dinosaur museum tucked in its basement.

These falls, sometimes called the "Niagara of the West," still put on a good show at the right time of year.

This set of hot springs also comes with fantastic views.

This highest peak in Idaho can only be reached by traversing a formation known as "Chicken-Out Ridge."

A petroglyph map of the upper Snake River carved by prehistoric hunter-gatherers.

A legal loophole makes it possible to get away with murder within this 50-square-mile section of Yellowstone.

These black pillars of volcanic basalt seem to call mountain climbers with an unbreakable siren song.

This museum glorifies the humble potato.

Home to the deepest rift anywhere on Earth.

Images chiseled into the basalt here date back an estimated 300 years.

Try your hand at old-fashioned coffee growing at this museum devoted to one of the world's most coveted beans.

This narrow coastline trail through the dense Kauai wilderness is among the most beautiful and dangerous in the world.

This unusual lava tube spouts seawater during high surf.