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

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

This cemetery features modernist statues as strange as its name.

This colorful statue welcomes visitors to a Barcelona park.

Barcelona's historic 19th-century sewers, whose foundations were laid in medieval times, are open to the public for exploring.

A beautiful but toxic fountain of mercury.

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

For one day every month Barcelona's Estació de França transforms into a market for model trains.

One of the most photographed buildings in a city known for its Modernista architecture is an abandoned squat.

Turntable anonymously received orphans, alms, and groceries.

The oldest giants in Catalonia are now displayed in a 14th-century Gothic church.

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

Historic medieval fortified city in southwest France.

A ship that lived many lives under many names is now known merely as the "Ghost Ship."

Walk in the footsteps of the gods and straddle two tectonic plates.

Eerie ruins of an abandoned medieval fishing village crumble atop an unforgiving stretch of earth.

Medicinal spa created with the discharge from a geothermal energy plant.

The somber sculptures commemorating Irish Famine on the river Liffey in Dublin.

Once the longest bridge in Ireland, this rusting span sits abandoned and overrun by nature.

One of the most popular megalithic sites in Ireland stands as a humbler version of Stonehenge.

The world of the ancient Celtic civilization explained through a bewitching 11 acre garden.

The ancient tomb acts as a calendar that keeps perfect time.

This Irish show cave is said to have been the site of a Viking massacre that claimed 1,000 lives.

An Irish church where an 800-year-old mummy is reaching out of his coffin as if to shake hands.