Three connected pink triangles memorialize persecuted gays and lesbians throughout history.

The world's oldest Jewish library was founded by Sephardic Jews in 17th century Amsterdam.

This city square is home to Amsterdam's oldest church and a statue honoring Dutch sex workers.

A beautifully eclectic mix of architectural styles.

The attic of a four-century-old canal house hides a clandestine church.

This historic Amsterdam bar used to accept sailor's monkeys as payment.

This gorgeous reading room houses the oldest and largest art history library in the Netherlands.

Established in 1638 to battle the Black Death, Hortus Botanicus Amsterdam is a treasure trove of rare flora.

The world's first zoo for microbes collecting the horrible and wonderful things living on and around us.

For decades, Puerta del Sol has been illuminated by a giant, guitar-wielding bottle of sherry.

The site of the deadly Triangle Shirtwaist Factory Fire.

An artist's cute bronze subway sculptures belie his violent artistic past.

A popular European tradition makes its way to the states on one of America's most famous bridges.

Ride the subways of yesteryear.

A three-story copper skybridge connects two Manhattan buildings with Art Deco luxury.

A room in New York City that contains 250 cubic yards of dirt worth a million dollars.

This sweet-toothed bear searching for snacks has been a symbol of Madrid for decades.

In the fictional world of Kcymaerxthaere, celestial wonders marked a portal to a powerful route of travel at this site in Madrid, Spain.

A lush indoor jungle fills this bustling Madrid transportation hub.

Over two centuries old and counting, Madrid's massive botanical garden contains one of Europe's only desert environments.

This macabre masterpiece of a mural is one of Francisco Goya's "Black Paintings."

Anonymously sculpted and donated, these sculptures made from poetry books and pages are sprinkled around the city.

This early version of the guillotine was used to execute the man responsible for its construction.

Near the former site of numerous witch burnings, this lavish Edinburgh mainstay pays homage to Scotland's brutal history.