A spring-fed pool so deep it's used for scuba diving as well as swimming.

An old railroad grade built for the construction of Hoover Dam is now a recreational trail featuring several tunnels and sweeping views of Lake Mead.

Experience a charming 1930s version of "infotainment."

A Norwegian-born sculptor created these soaring guardian angels at the entrance to Hoover Dam.

These markers are used to document elevation changes around the famed dam.

Beehive charcoal kilns and slag deposits mark this late 19th century camp centered on a smelter.

Visitors to this arboretum are greeted by three smiling giants crafted from sustainable materials.

So many migrating birds roost on the bridge, it has a special summer speed limit.

The world's longest known cave system.

An idyllic mineral hot springs facility with a more-than checkered past.

Enormous lake at the bottom of a unique cave system.

A rotting tree in the middle of Seattle doubles as an elaborately-controlled art piece.

This dilapidated ship carcass covered in trees is a striking sight.

On the edge of this small Washington Park, a piece of the Earth's mantle has come to the surface.

A giant sculpture dedicated to a staple of South Bend food culture.

Essence of hound's tongue and tincture of bloodroot are just the tip of the herbalist iceberg at this beautiful, impressively-stocked apothecary.

These memorials built by an eccentric bachelor on the side of Interstate 5 cause both wonder and traffic accidents.

This ancient village provides insight into the complexity of the pre-Columbian Fremont Culture.

This now-abandoned part of the original transcontinental railroad route provides a surreal driving and historical experience.

An impressive waterfall nestled in the cliffs of Idaho's Snake River Canyon.

Stroll through a wonderland of stupendous moss-covered trees.

Inside this striking glass building, visitors can see thousands of dinosaur fossils in the positions that nature deposited them more than 150 million years ago.

This Moab institution functions as both a rock store and a small natural history museum.

A river runs through this remote valley in a very unexpected way.