The narrowest street in Paris.

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

The very center of Paris is surrounded by a bevy of strange good luck rituals.

An expansive complex of subterranean tunnels is all that remains of one of Europe's most formidable medieval fortresses.

This outdoor library provides around-the-clock access to around 7,000 books.

This natural hill rose another 130 feet from the debris and rubble added after World War II.

The last of Amsterdam's original sea level markers remaining in place.

Famed for its pie, this eatery has a hidden tunnel that allowed Catholics to secretly walk to church during the Reformation.

A unique collection of gilded age mechanical pianos.

Seven mini rowhouses fill the gap between 54 and 70 Westerstraat.

Tucked in the back of a flower shop, its collection details the fascinating history of the Netherlands's iconic symbol.

This cheese shop also houses a museum devoted to Dutch dairy.

Europe's first floating restaurant is home to a hilarious legend.

This 22-floor tower's Skydeck offers panoramic views of Amsterdam.

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

One of Amsterdam's narrowest houses is located right across the canal from its widest.

The history and future of cannabis.

The facade of this bank has changed little over the centuries, including its unique welcome sign.

A hidden church in a hidden courtyard tells the story of the Miracle of Amsterdam.

In the days before house numbers, these colorful signs held clues about various buildings' purposes.

A floating cat sanctuary on an Amsterdam canal.

Amsterdam's narrowest house facade is a monument to 17th-century tax evasion.

A Dutch passageway's artistic, aquatic-themed makeover pays tribute to the capital city's famed waterways.

A cableway for car transport.