18th century anatomical amphitheater of the Royal College of Surgery of Barcelona.

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

A once-secret library of Freemason history in Catalonia.

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

The studio of Catalonia's most famous theatrical designer remains exactly as he left it.

One of Europe's largest supercomputers is housed inside of a disused chapel.

This Funeral Hearse Museum represents the finest in cadaver transportation.

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

A stately palace has been converted into the world's largest cannabis museum.

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.

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

Bask in the 19th century grandeur of an eccentric Freemason millionaire's private gardens.

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

An unusual stroll through gentlemen's erotica demonstrates that pornography is timeless.

Mountain where Jesus was first tempted by the Devil.

This cemetery features modernist statues as strange as its name.

These secluded and abandoned anti-aircraft defenses have become one the most scenic viewpoints in Barcelona.

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

A beautiful but toxic fountain of mercury.

This semi-secret storybook hedge maze is also the oldest garden in the city.

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.

Legend has it this gnarled old tree was planted by Tsar Peter the Great during his visit to London.

The final resting place of a German diplomat's beloved companion.