Downtown Minneapolis mixed art and function by turning some of their sewer covers into works of art.

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

A spiritual vortex among the red rocks in Sedona.

An urban laboratory.

The last remaining relic of San Francisco's glittering 1915 Panama Pacific Exposition.

A collection of 20th-century automata, penny arcade games, and musical contraptions.

This concrete tangle of square pipes has stood as a proud thorn in the city's side since the '70s.

San Francisco's newly reopened hands-on science museum.

This private residence was the template for one of the most beloved television homes of all time.

Not merely a museum – but a whirring powerhouse that offers a subterranean peek into the heart and soul of cable car operations.

This simple stone memorial remembers a secret, Geneva Convention-defying interrogation base from WWII.

The water-powered carriages are long gone, but for over a century this funicular railway has been the fastest route to the highest point in Paris.

An underground city of salt.

The celebrated eyesore created by starry-eyed sweethearts.

Ancient serpentine sacrifice holder that has stood the test of time.

A marvel of Byzantine engineering under the streets of Istanbul.

The oldest working mechanical clock in the world.

The crypt of the imposing Stephensdom holds royal intestines and thousands of skeletons.

The most loyal of little dogs, or a Victorian era publicity stunt?

17th century streets hidden under Edinburgh were once a breeding ground for the black death.

One of the tallest buildings in Iceland, and perhaps, the most visually impressive.

This short bridge is the only thing connecting a tiny Irish island to the mainland.

Virgil's many-mouthed gateway to the underworld.

Concrete crosses scattered across the Arizona scrubland which were used to align spy satellites.