The industrial architecture honors the laborers who brought the Exposition Universelle of 1900 to life.

135 bronze medallions mark a French meridian line which once rivaled the hotshot Greenwich timeline.

At the crypt of St. Mary of Eulogies and the Dead you are left alone to ponder mortality among piles of skulls.

For centuries no one knew there were hundreds of bones and precious artwork hidden beneath this Swiss church.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

The floorboard scrawling of a tragic madman is on public display outside a Paris hospital, much to the dismay of its opponents.

The man who introduced reinforced concrete to the world demonstrated its genius by using it to build his own house.

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

Skeletons, medical artifacts, and other obscure and precious treasures all displayed in a wooden pharmacist's cabinet.

Collection of antique taxidermy and natural specimens, near one of Paris's oldest flea markets.

An iconic and eccentric bar for "Manouche" Jazz music keeps expanding its space—and its influence.

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

This Parisian café sticks almost exclusively to an ethos of reuse.

This hidden workshop is filled with molds of France's most iconic sculptures.

The mummified heart of Louis XVII, the lost dauphin of the French Revolution.

The tradition of open-air secondhand and antiquarian bookselling in Paris dates back to the Renaissance.

The narrowest street in Paris.

The underground sanctuary of a mysterious ancient cult.

Architectureal fantasy quarter of Rome.

The final resting place for the remains of 143 Habsburg royalty.

Dedicated to an "Unknown Man," this grave holds either the remains of a lovelorn suicide or a Cold War spy.

The most visited, and possibly most controversial, museum in Germany.

Repository for more than 22 million pickled specimens.

Natural rock formation, or biblical artifact that saved Earth's wildlife two by two?