This geothermal hot spring hides beneath a slowly growing mineral dome.

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

This frequently-photographed waterfall takes only a short hike to visit.

These delicate buggers are some of the rarest fossils that have bubbled up from the Tar Pits.

Take a drunken tour inside the world's largest known geode.

A favorite haunt of dinosaur loving children and hallucinogen loving hippies alike.

An underwater city for the dead.

This naturally-sourced hot spring is now home to a clothing-optional resort.

A self-built castle made by a mysterious man.

This unique structure in suburban Austin is made up entirely of other people's castaways, and constantly changing.

A beautiful geyser under environmental threat.

Seemingly grown on some other world, these New Mexico rock formations look like a disused science fiction set.

A breathtaking array of ancient Pueblo structures and artifacts counterintuitively preserved by neglect.

A trash dump made beautiful by nature's power.

The first declared National Monument in the United States.

This abandoned amusement park was built on a site with a dark history.

Where manatees are the snowbird vacationers in these balmy Florida springs.

Mysterious rocks that ring musically when struck.

The hike through a narrow river flanked by the 2,000-foot-tall walls of Zion Canyon is one of the best in the world.

Ninety feet off the valley floor is an ancient dwelling put under protection of the U.S. government by Teddy Roosevelt.

Stepping away from the glitz of mobsters and casinos to learn about the other history of Vegas.

The deepest lake in the United States, and once the site of epic destruction that lives on in legends.

The only theatre in the world constructed specifically for sound movement.

Home of an evil witch famous within southern folklore.