148 feet long and in the middle of a verdant forest.

The hotel where Martin Luther King Jr. was shot is now a museum dedicated to his work.

This large midwestern cavern features impressive rock formations and an underground waterfall.

Every equinox this Maya pyramid puts on a spooky ancient light show.

The first park built over a freeway is a brutalist masterwork.

This Colorado hiking trail provides a small gold mine of abandoned gold mines.

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

Despite being one of the most photographed vistas in the Rockies these twin peaks are rightfully known as the "Deadly Bells."

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

This replica of the Greek structure is in the heart of Nashville.

This popular bar has been blurring the line between normal and edgy for more than 75 years.

A luxurious 1880s hotel with its fair share of Tiffany stained glass, Edison electricity, and of course, ghosts.

At this Denver landmark, the meals are compulsory, the sopapillas are complimentary, and the insanity is everywhere.

A multi-storied adobe complex has been inhabited for more than a thousand years.

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

The superstar of Cold War nuclear bunkers has been featured in countless films but is now barely operational.

The remnants of two World's Fairs are here, complete with a 12-story globe, a mini-Manhattan, and a UFO-shaped pavilion.

A house carved into a rock in the 1940s.

A striking 12th-century-style castle built on the edge of a cliff.

Legends surround this jagged rock formation in the New Mexico desert.

When ecosystems collide in the arid Southwest.

The highest bridge in America was built for an almost unnervingly small amount of money.

A sculpture made of 10 Cadillacs as a monument to the "Golden Age" of the American automobile.

This statue was given to France by the United States to commemorate the centennial of the French Revolution.