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

Bizarre lunar-like landscape with thousands of large stone "hoodoos."

An earthwork sculpture built by Robert Smithson in the Great Salt Lake only reemerges during drought.

This rugged area of red rocks and arches is often considered one of the most beautiful places on Earth.

The only retired U.S. nuclear missile silo that is open to the public.

A popular rock that acted as a waymarker for American pioneers.

A monument to the egos of two railroad magnates that fell into decline along with their careers.

This rustic old building is said to be the most photographed barn in America.

Miraculous tree that seems to sprout out of solid rock.

This Yellowstone geyser may not shoot as high as the nearby Old Faithful, but it erupts for considerably longer.

The only natural lake in the world that drains into both the Atlantic and Pacific Oceans.

Devilish landscape, once cinema home to giant alien bugs, now derelict roadside attraction.

One of the smallest towns in the United States.

An architect's childhood fantasy treehouse made real.

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

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

A beautiful geyser under environmental threat.

The first declared National Monument in the United States.

When ecosystems collide in the arid Southwest.

Explore the largest pure gypsum deposit in the world, and go dune sledding while you're at it.

An immersive environment that is part haunted house, part choose-your-own-adventure, and part jungle gym.

A museum dedicated to the alleged Roswell Incident.

This secluded aqua waterfall in the Grand Canyon is the perfect swimming hole, and the Havasupai tribe's fiercely protected natural wonder.

Dramatic river bend surrounds a natural red-rocked pedestal.