Longest road tunnel in the world features an air treatment plant and the illusion of daylight.

This woodland architectural installation acts as a camera obscura for the heavens.

This outdoor gallery of graffiti-covered walls pays homage to the past, present, and possible future of street art.

This probably wasn't what Mao had in mind.

Large collection from the 3rd millennium BCE.

This remarkable cave was discovered after a shepherd watched bees enter and exit through a small fissure.

A minotaur, a labyrinth, and a dubious restoration pull in visitors from around the world.

The intricate stonework of Machu Picchu serves as a testament to Incan engineers.

Climb inside an iron crystal magnified 165 billion times its normal size.

An artist's cute bronze subway sculptures belie his violent artistic past.

A museum dedicated to the history and exploration of both popular music and science fiction.

The Denver airport is guarded by a 32-foot-tall sculpture of a demonic horse.

The second-largest cave chamber in the world was discovered in 1898 by a 16-year-old and a friend known as "Pothead."

A museum dedicated to the alleged Roswell Incident.

The last remnants of what was once one of the world's grandest hotels can now be found in a Manhattan subway station.

A Manhattan courthouse hides a small but scathing memorial to Holocaust injustice.

The sound of swaying stalks in this stunning grove has been named a governmentally recognized sound.

The highest point in Tennessee, Clingmans Dome bears witness to the ravages of one type of insect.

This shifting North Carolina sand dune is an odd little desert surrounded by oceanic forest life.

Open-air museum with an elaborate sculpture garden, stretching for over 70,000 square-meters.

The most famous location in China was home to whole dynasties worth of imperial rulers.

Legend holds eating just one of these black eggs can add seven years to one's life.

This historic address is home to the beloved ball and is an almost totally empty building among the most expensive real estate in the world.

There must be a pun in this haystack somewhere...