400 million-year old limestone caverns nestled in the Ozarks served as shelter and a hideout for cultures throughout North American history.

America's silhouette includes 100 square miles of wilderness jutting into Canada thanks to an old mapmaking error.

This Minnesota town celebrated the state's 100-year anniversary by creating a massive ode to nature's smartest bird.

Equal parts record-breaking temple to consumerism and bizarre fun park, it's more than you think it is...

This large midwestern cavern features impressive rock formations and an underground waterfall.

A pop-culture attraction outside of Dyersville, Iowa, hits a home run.

The longest navigable underground river in the United States is home to countless blind and albino animals.

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

This once-booming Gold Rush town is now home to a herd of feral donkeys.

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

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

Dyed by iron oxide over centuries, these sandstone rocks rise thousands of feet into the sky.

Two geoglyphs that are truly unique to North America.

A series of labyrinths in the Nevada desert inspire meditation and calmness.

Visitors can walk over the largest concentration of Columbian mammoths to have died from one event.

The Grand Canyon of Texas.

The future of roadside attractions is this sci-fi soda mecca that is home to a 66-foot tall neon pop bottle.

The sweetest graveyard in the world is filled with headstones for dearly de-pinted ice cream flavors.

As state high-points-by-elevation go this spot is one of the lowest, but for years it was also the hardest to climb.

Ironically this massive termite is the mascot for a company that is acclaimed for killing his kind.

Three and a half miles of cliffs, rocky beaches, Gilded Age mansions and 40 Steps to nowhere in particular.

A serene plaza that commemorates one of the Granite State's most iconic figures.

Even Henry David Thoreau found this glacial pothole irresistible.

A former waterfront market is now in the center of town due to some interesting Boston engineering.