This cave holds a surprisingly colorful variety of geological oddities.

Vikings and Evangelicals have both had a hand in this replica medieval church.

These Great Lakes sea caves accessible by boat in the summer turn into temples of ice reachable by foot in the winter.

One day a year it is legal to jump off of this astoundingly tall bridge that spans an Appalachian gorge.

The longest continuous lava tube in the continental U.S. offers 2.5 miles of dark explorations for the adventurous.

A sacred site for Native Americans surveyed by George Washington and owned by both King George III and Thomas Jefferson.

A 300-yard long natural tunnel runs through a ridge deep in the Appalachian Mountains.

An ancient glacial pothole waterfall in the heart of the Green Mountains.

The largest island on the great salt lake is home to curious creatures and strange stories.

Despite its name, this route in southern Utah offers a heavenly day trip.

The marker offers a rare chance to be in four U.S. states at once, though there's some controversy over its geographic accuracy.

A house carved into a rock in the 1940s.

Giant, natural amphitheaters made of delicate geological formations called "hoodoos."

Here, at the "world's longest art gallery," you'll find forty miles of ancient petroglyphs and pictographs.

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

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.

A Texas museum filled with Broncos and Betties.

A popular swimming hole that hides one of America's most deadly diving spots.

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

This large cave is a summer home to thousands of bats and has a rich history dating back to prehistoric times.

The first full-scale tunnel built in America is short but scenic.

All you ever needed or wanted to know about America's favorite whiskey, but not a drop to drink.

Enormous lake at the bottom of a unique cave system.

The ravine where Jesse James supposedly performed an impossible jump to evade capture.