The "Greatest Sewer" of ancient Rome is one of the oldest sewer systems in the world, and is still in use.

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

A beautiful Victorian statue shows France's enduring love of the rhinoceros.

This bridge was constructed from the rubble of the infamous Bastille.

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

A surrealist timepiece by the artist of melting clocks.

An early 20th-century bullring converted into a modern shopping center.

A once-secret library of Freemason history in Catalonia.

Gaudí's famously flamboyant architectural style is on full display in this sprawling park and garden.

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.

One of Antoni Gaudí's most classic buildings is well-known for its "dragon-back" design.

The largest bell in the world has been swinging high above a Cologne cathedral for almost a century.

Home to three historic ships from the age of Vikings.

Across the Pacific in a raft, a museum dedicated to Thor Heyerdahl's now legendary expedition.

One man's exploration of the human form, including the bizarre and delightful "Man Attacked by Babies."

In downtown Oslo, a menacing and terrifying relief clings to a church wall.

The design of this beautifully crafted building was inspired by Norwegian glaciers.

The Brutalist building harbors an unusual inverted dome that swoops down over its central sacred room.

This floating sculpture of ice is a poignant reminder of nature's power.