Giant topiary dog once played a role in a terrorist bomb plot.

Two towns are linked by an engineering marvel masquerading as a boring suspension bridge.

Raging waters have created a strange geological site that looks like something off of a progressive rock album cover.

This Roman arena once played host to bloody gladiatorial battles.

Touching the iron railings of Tarragona's balcony to the Mediterranean is said to bring good luck.

Mountain where Jesus was first tempted by the Devil.

A former steam-powered mill from the 1800s is now an industrial park with a giant steel dragon slide.

This colorful statue welcomes visitors to a Barcelona park.

Dunk your churros in rich hot chocolate on the city’s old “Chocolate Street.”

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.

One of Antoni Gaudí’s earliest buildings, built between 1886 and 1890 for the industrialist Eusebi Güell.

It’s Christmas every day at Barcelona’s oldest restaurant.

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

Cursed swimming pool left abandoned is now a favorite of filmmakers and ghost hunters.

This imposing modern citadel started out as a home renovation project.

This chest hospital with a dark, haunted past serves as a fitting set for horror films and a paradise for ghost hunters.

The Gaudí-inspired building that was the start of Terrassenc modernism.

A gravity-defying "devil's bridge" that has a surprising architectural feature for its stability.

Holy Grotto of Montserrat Monastery holds one of Europe's mysterious black Madonnas.

Designed by Gustave Eiffel before his famed tower.

Village situated on a narrow volcanic escarpment.

Religious dwelling in a Spanish volcano.

In this tiny Iranian town playing on the roof isn't just encouraged, it's the only place to go.

This 17th-century structure is a beautiful testimony to traditional Persian architecture