An overlooked marble is the only surviving in-place 18th century example of the measurement that changed how we define distance.

The first green space constructed on an elevated viaduct.

A Parisian cemetery where the elite and artistic are interred beneath an eccentric collection of tombs.

19th century pendulum and a clock restored by a rogue group of guerilla artists.

An "inside out" building in the historical center of Paris, featuring Europe’s largest modern art museum.

France's national museum of scientific and industrial instruments.

A raised boardwalk winds through a thicket of stunted, century-old trees no more than nine feet tall.

A unique botanical garden housed in three giant geodesic domes.

A library and museum dedicated to typography.

Stroll through retro Paris while shopping for old postcards and discarded doll heads.

A walk-in working camera obscura produces 360-degree live images of the San Francisco coast.

The seawater playground of gilded-era San Francisco burned to the ground in 1966.

This painted marvel is San Francisco's 400-foot ode to urban biking.

Funhouse of found art and participatory sculpture.

A museum celebrating the self-taught artist-environment builder.

This demon atop the Notre-Dame de Paris looks utterly bored.

Restaurant in Northern Wisconsin comes with a unique feature: a grassy roof covered in living goats.

Odd outsider art installations surround a Gold Rush-era ghost town.

Bring your own cardboard to the slippery slopes of concrete hidden in a neighborhood park.

A small peaceful park and waterfall tucked amid the urban grind of Midtown Manhattan.

A hugely vast Irish landscape of barren rock that stretches for miles.

One of the largest aviation events in the world brings half a million aircraft enthusiasts to Wisconsin each year.

The home of 1.5 million wood letters for printing is still a functioning workshop.

A colorful architectural gem in Seattle's uniquely modern Central Library.