These 2000 year old remains of a Roman aqueduct are hidden inside a hotel lobby.

This home designed for chocolate magnate Antoni Amatller is an exquisite treasure-box of Catalan Modernism.

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.

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

This former Baroque palace on the historic Calle Montcada is a rare architectural gem and was once the meeting place of an aristocratic scholarly society.

Gaze upon chocolate sculptures depicting everything from chariot races to Gaudí's famous church at this shrine to sweets.

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

The 2,000-year-old Roman columns are hidden within Barcelona's Gothic Quarter.

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

Designed by Gustave Eiffel before his famed tower.

Of course Salvador Dalí lived in a castle...

Giant eggs, walls of bread, and nightmare surreality mark the largest collection of works by Salvador Dalí.

The site of the first medieval crusade that pitted Christians against Christians.

Historic medieval fortified city in southwest France.

Half a century after it was abandoned, this ghost town is coming back to life.

This army of concretions is an unexplained geological phenomenon unlike anything else in the world.

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

A chapel on a volcanic core, marking the end of a successful journey.

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

The remains of this castle, known as the Witch’s Eye, watch over the Thur Valley.

One man's stunning attempt at eco-friendly living.

This small chapel built into rock is the oldest place of worship in Luxembourg.

This magenta statue commemorates the legendary marriage between a mermaid and the city's founder.