This huge dam across the Colorado River caused an armed standoff between two U.S. states.

A pair of giant roadside arrows are all that remains of a former Route 66 trading post.

This public square capitalized on a single Eagles reference to bring some life back to an Arizona town.

This immigrant bridge once spanned the Thames but is now a fixture of an Arizona city.

Some of the tallest ancient American ruins continue to inspire awe and curiosity.

America's only nuclear missile silo open to the public.

Dramatic river bend surrounds a natural red-rocked pedestal.

Ninety feet off the valley floor is an ancient dwelling put under protection of the U.S. government by Teddy Roosevelt.

The final resting place of the businessman-turned-astronomer who helped discover Pluto stands near his observatory.

The highest point in Arizona is an oddly snow-topped peak within the otherwise arid state.

This Arizona observatory is famous for investigations into Martian life, and as the place humans first spotted Pluto.

Ancient pueblos built into the base of a natural canyon wall.

This historic national park is covered in the stunning ruins of red rock pueblos.

A hillbilly theme park that proved so unpopular the land wouldn't even sell on eBay after it closed.

A 35-foot-tall fork stuck in the ground outside an office building in Missouri.

The remains of a World War II-era Japanese American internment camp dot a windswept Colorado hill.

This underfoot portrait is the work of a disgruntled painter inspired by a tragic poem.

The fifth-longest natural arch in the world, and the longest outside China.

An enthusiastically interactive mining museum that won't let black lung ruin the fun.

A 90-foot-tall psychedelic "tree" on the side of the highway has baffled passersby for decades.

Hidden inside this Arizona fast food franchise is an in-depth exhibit on the famed WWII counterintelligence program.

One of the world’s largest collections of petroglyphs records 2,000 years of human activity.

This reclusive Hopi village in Arizona has been continuously populated longer than anywhere else in America.

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