Rusting, graffiti-covered tanks litter the beach of this island, once used by the U.S. military for target practice.

This beachside town is home to a diverse nature reserve, multiple cays, and one of the three bioluminescent bays in Puerto Rico.

The second-largest cave chamber in the world was discovered in 1898 by a 16-year-old and a friend known as "Pothead."

The highest point in Texas is capped by a big silver pyramid.

The fifth-longest suspension bridge the world, connecting one Michigan peninsula to another.

These dramatic cola-colored falls have appeared in a poem by Henry Wadsworth Longfellow and a song by Sufjan Stevens.

Island where motor vehicles are banned -- home to the only carless highway in the United States.

An impressive collection of over 50,000 minerals including moon rock from the Apollo 17 mission.

This three-mile concrete levee in Pueblo, Colorado was transformed into the world’s longest painting.

The Grand Canyon of Texas.

A 200-year-old building in the French Quarter that was to be Napoleon's home in the New World.

This cathedral dedicated to Louis IX, sainted King of France, holds many secrets.

A sandstone canyon wilderness with a history of outlaws, mysterious disappearances, and a UFO encounter.

An immense cave that has served as an outlaw's treasure trove, an underground dance hall, a nuclear fallout shelter, and much more.

An emerald-green grotto just a short trip from Austin.

The tree is thought to be the oldest oak in Texas and was once crowned state champion for its monumental size.

This Texas windmill field celebrates the power and majesty of the very winds that blow.

Over 100 million years ago, beach-bound dinosaurs left permanent marks on San Antonio's landscape.

Water still flows through the oldest Spanish aqueduct in America.

Three hundred years of preserved Spanish colonial history in San Antonio.

Colorful curls of hand-blown glass form a captivating tower in San Antonio's Central Library.

Craggy concrete faces are hidden in the walls of this artificial cave along the San Antonio River.

A gorgeous garden oasis with winding paths, stone bridges, and a troubling history.

One of the highest points in Bexar county offers birdseye views of San Antonio and a four-story stone tower.