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

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

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

This cemetery features modernist statues as strange as its name.

A beautiful but toxic fountain of mercury.

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

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

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

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

Unsurprisingly, Holland is home to one of the most magnificent flower gardens in the world.

Oldest Museum of the Netherlands is a true cabinet of curiosities.

An Amsterdam street lined with antique shops each one dedicated to a different obscure collection.

Established in 1638 to battle the Black Death, Hortus Botanicus Amsterdam is a treasure trove of rare flora.

The world's first zoo for microbes collecting the horrible and wonderful things living on and around us.

This basement museum explores the art and artistry of fascism.

This historic Amsterdam bar used to accept sailor's monkeys as payment.

A 'living museum' in Leiden, the oldest of its kind in the Netherlands.

Strange secondhand shop showcasing taxidermy and oddies

Peek through a transparent pyramid and drink in the mountain made of books.

This ghost town in Belgium will lose its street art when it ceases to exist.

Housing the groundbreaking maps and globes of Gerard Mercator.

An undulating wicker beast looms peacefully atop a sand dune in Belgium.

This tri-part waterfall is a little bit of fairytale beauty in the heart of Luxembourg's Little Switzerland.

Once the local rulers had gone these enchanting ruins housed common folk in an almost real life fairy tale.