The world's largest man-made underground caverns offer unparalleled underwater wonders.

The history of the treatment of mental illness, illustrated in all its gory detail, and housed in an asylum.

If there's another drive-through golf-cart bar in a bat-filled cave on top of a mountain, we don't know about it.

This abandoned prison castle has become an imposing gallery of graffiti art.

Less a museum than a bizarre fantasy world created by artists and engineers.

European castle ruins in an American state park are actually the product of death and grief.

This pristine World War II airfield gives a comprehensive look at atomic development and aviation history.

The natural history of Utah is on full display inside this museum.

A volcanic core jutting above the plain between the Snake and Boise Rivers, a marker identifies the reference point for all U.S. Government Surveys in Idaho.

Cross the Continental Divide through an old railroad tunnel, and ride back to the top on a shuttle.

The only bridge in the United States where BASE jumping is legal without a permit year-round.

A former sanitarium where soldiers were sent to recover in the healing waters of hot springs.

A miner's handmade folk art fountains are tucked in the woods off a multilane highway. 

One of the "twins" in these falls on the Snake River was sacrificed for hydropower generation in the 1930s.

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

This underground cave located in the most barren reaches of Idaho is filled with ice year-round.

This work of art by Matthew Mazzotta resides in this park dedicated to the first black legislator in Idaho.

This giant tower beacon was a key navigation tool for pilots delivering mail amid the night skies.

Boise State's stadium was the first non-green football field in the world.

New Plymouth, Idaho is the only U-shaped town in the United States.

This combination shop and museum is filled with curious items and artifacts.

Where the famed daredevil attempted to launch himself across a canyon in a custom-built rocket.

Tucked away on a scenic trail, a modest memorial honors one of the greatest writers of our time.

Three generations of intrepid collectors display their curious artifacts in a homemade museum right next to the caves they discovered.