20,000 pieces in a Frank Gehry-designed building.

A turn-of-the-century architectural marvel built on healing mineral springs and salt licks.

A stunning, abandoned limestone quarry in southern Indiana provided the stone to erect the Empire State Building.

A tribute to the Polish insurgents who fought in the failed attempt to end their city's Nazi occupation.

Famously misunderstood wonder of the ancient world

Built by a king and rebuilt by an emperor, this aqueduct transported water for 1,200 years to this ancient Mediterranean hub.

Twenty-seven massive radio antennas on the high plains of New Mexico search for life on other planets.

This is one really big nut.

A clear blue swimming hole with hidden caves, still unexplored.

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

The rocks of a certain area of Butte, Montana give off a musical ring when hit.

Clap your hands at the base of the pyramid, and the song of a sacred Mayan bird will echo through the air.

Underwater art project will double as a massive artificial coral reef to help regenerate the damaged ecosystem.

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

This Industrial Age architectural and engineering gem helps visitors and residents alike traverse Lisbon, “The City of Seven Hills.”

An ancient and majestic fortress that played an integral role in Portugal's road to independence.

A king's pet, a pope's gift, an artist's inspiration, and a tragic shipwreck.

This unreal Portuguese palace looks as though it's made from a pile of different castles.

Legacy of the earthquake that nearly wiped Lisbon off the face of the Earth.

The Old Courthouse takes visitors on a captivating trip through St. Louis' timeline.

Giant granite rocks standing end-to-end like a train of circus elephants.

A dramatically eroding canyon thousands of miles from the desert.

An eerie and beautiful group of columns mark the site of a grand mansion lost to time and fire.

The Dover International Speedway is home to a towering, concrete-skinned, racecar-hungry behemoth.