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

The iconic boulevard is the perfect place to catch sight of a bicycling skeleton, a levitating Satan, or a chef with his head stuck in a pizza.

The largest Art Nouveau complex in the world is a Barcelona hospital with a 600-year-long history.

A vista of the city and sea from atop the little-known viewing deck on an unassuming Columbus statue.

Step inside the first house designed by Catalan architect Antoni Gaudí, considered to be one of the first Art Nouveau buildings.

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

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

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

Lyon's miniature version of the Eiffel Tower was built as a statement in support of French secularism.

An effigy of a trapped paratrooper dangles from a Normandy church to commemorate one remarkable D-Day event.

This church sits upon a peaceful hill and a long, turbulent history.

One of the most powerful religious centers in the Middle Ages, dubbed the founder of Western monasticism.

A Christian retreat founded to welcome refugees fleeing from the Nazis during World War II.

Beneath the city of Lourdes, France is a massive, concrete church.

A colorful piece of contemporary art cheerfully clashes with Lyon's historical architecture.

Walk through living pictures and music in the Cathedral of Images.

Even France's favorite aquatic son Jacques Cousteau, couldn't get to the bottom of it.

A medieval church with largest and oldest collection of Renaissance frescoes in France.

An ancient ossuary in Rouen.

Despite centuries of architectural innovation, this French castle is being built like it's the 13th century.

The water-powered carriages are long gone, but for over a century this funicular railway has been the fastest route to the highest point in Paris.

Lyon, France is home to two remarkably preserved Roman theaters, one dating back to 15 BCE.

This ancient Roman bridge and aqueduct still stands as a wonder of classical construction.

A natural arch carved by a river gave its name to the so-called "Cave of Forgotten Dreams."