A modernist landscape of water and sci-fi concrete.

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 huge musical sculpture and other art installations on the National Oceanic and Atmospheric Administration grounds.

A self-built castle made by a mysterious man.

This 4,000-foot-diameter hole is touted as "the most well known, best preserved meteorite crater on Earth."

The land is full of geologic eye candy, such as otherworldly spires, mushroom-shaped hoodoos, and prehistoric fossils.

The largest hot spring in the United States is, as the name suggests, a stunning show of natural color.

One person's lost luggage is another person's treasure.

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

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

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

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

An underwater city for the dead.

Behind this beachfront shop lies a spectacular, colorful sea cave with an equally colorful past.

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

An abandoned facility that has become a place of ritualistic satanic worship, or so rumor has it.

Rainbow-hued local gem in Venice.

This abandoned asylum was once a state of the art facility before devolving into one of the most deadly mental institutions in American history.

A pair of slides and a tree-lined stair corridor have been an urban oasis for nearly 40 years.

This strange seaside tower got its name from a wealthy eccentric who would hide coins among its stones.

A stunning, two-tiered waterfall made famous by poets, artists and the legend of a ghost dog.

New York City's smallest piece of private property.

Hollowed out cedar log tubs set in an ancient towering forest.

Where America's first doomsday cult awaited the end of the world.