A beautiful geyser under environmental threat.

The first declared National Monument in the United States.

More than 5,000 contemporary and "historic" mustards from around the world.

This cave holds a surprisingly colorful variety of geological oddities.

A bizarre house filled with an astounding array of collections.

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

On the Fourth of July this area will transform into a Pompeii-like storm of falling embers and ash.

The famous abolitionist’s preserved estate is one of Washington's finest monuments to its great Black citizens.

A lovely aquatic park built by a one-armed Civil War veteran who made a fortune from lotuses.

A 1940s nuclear reactor built to produce plutonium for the Manhattan Project.

Nuclear reactor created the plutonium used on Nagasaki.

The highest point in Washington state is a volcano covered in glaciers.

A wall of chewing gum moonlights as collective art.

This isn't your average roadway—it's actually a National Park and a transportation pioneer.

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

This raised bulls-eye visible from space was the subject of an intense geologic controversy.

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

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

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.

Belly up to the bar in Cowtown, don't forget to buy some boots.

This downtown Dallas art installation is always on the lookout.

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

The Grand Canyon of Texas.

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