The hallowed remains of a 900-year old Ancestral Pueblo great house.

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

The unusual patterns in this rock formation result from two distinct modes of weathering.

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 tunnel with windows, so you don't miss out on the impressive views.

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

The first declared National Monument in the United States.

Dedicated to the history of the 1,000 nuclear missiles that once covered the Great Plains.

The granddaddy of all tourist traps, built on ice water, jackalopes, and a giant dinosaur.

The world's largest mountain carving could fit all of Mount Rushmore inside it many times over.

A memorial to the most decisive Native American victory of the Plains Indian War.

An entire town preserved as a historic landmark.

One of nature's most well-scheduled phenomenons resides in Wyoming's Yellowstone National Park.

A beautiful geyser under environmental threat.

The mayor made the declaration in 2004.

Two mammoth statues inspired by equally tall tales lure tourists to this roadside attraction.

An obscure waterfall that looks like something out of a fantasy novel.

The sail of the first nuclear sub to circumnavigate the world.

One of two observatories in the U.S. that routinely detect gravitational waves.

Nuclear reactor created the plutonium used on Nagasaki.

The strange phenomenon causing gravity to "work backwards" on this hill has been blamed on the paranormal.

This metallic stampede sits frozen on a Washington ridge yet the artist's vision is still incomplete.

One small town in the Pacific Northwest transformed itself into a Bavarian-themed tourist destination.

Perhaps the world's only gas station inspired by a political scandal.