This frog-themed restaurant was frequented by Picasso, Saint-Exupéry, and more.

A counter-culture bookstore like no other hides in plain sight in the streets of Paris.

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

Legend says it was constructed with the destroyed pillar of an ancient Greek Temple.

Gladiators once walked this ancient, subterranean passage.

The Cycladic architecture makes this Athens neighborhood feel like an island paradise hidden in the shadow of the Acropolis.

A 2,000-year-old computer demonstrates remarkable engineering and astronomical precision.

The topiary maze at the Habsburg hunting lodge.

The beautiful baroque library of the Hapsburg empire.

Outstanding taxidermy dioramas showcase the grandeur of the continent's wildlife with spooky realism.

The mosaic Star of David at the front of this store hints that it's no ordinary Italian grocer.

This enormous banquet-themed artwork honors over 1,000 notable women throughout history.

The first piece of public art dedicated to LGBT rights.

This exemplar of modernist architecture is meant to captivate and inspire students of the Cooper Union.

Phil Mortillaro uses keys to bring art back to the Village.

One of the oldest Jewish cemeteries in the city, it is now overgrown with an urban forest.

A dark patch of the ceiling at Grand Central Terminal which was not restored is still stained brown by tobacco.

Every year model trains zip through a miniature New York City that's now 150 landmarks strong.

The notorious headquarters of a corrupt political machine.

In its day this historic fort held 100 cannons pointed in almost every direction to protect New York.

Commemorating the spot where the famous scientist fed his pigeons.

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

America's oldest Eastern European synagogue provided the immigrants of crowded Lower East Side tenements a space of sanctuary.

A curious fountain that has no water and includes Satan, a crab, and 9 giraffes.