A private collection of massive steel monsters guarding a Texas pipe works.

A little bit Wonkatania, a little bit pink elephant.

One man's homage to the orange as realized through a long-term folk art labor of love.

An expansive complex of subterranean tunnels is all that remains of one of Europe's most formidable medieval fortresses.

The birthplace of Karl Marx is now a museum dedicated to the communist revolutionary's life and work.

Madrid's romantically ornate crystal palace has been offering shelter to plants and art for over a century.

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

Mountain where Jesus was first tempted by the Devil.

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

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

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

A vista of the city and sea from atop the little-known viewing deck on an unassuming Columbus statue.

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

This former Masonic lodge has been transformed into part museum, part bar, all awesome.

This 22-floor tower's Skydeck offers panoramic views of Amsterdam.

A floating cat sanctuary on an Amsterdam canal.

This basement museum explores the art and artistry of fascism.

The attic of a four-century-old canal house hides a clandestine church.

Amsterdam's Red Light District leaves little to the imagination.

A beer pipeline runs beneath Bruges.

This narrow Ghent alleyway is an officially sanctioned street art tunnel.

An open-air sewer system that was covered piece-by-piece over 300 years.

Theme park featuring miniature replicas of European monuments.

Climb inside an iron crystal magnified 165 billion times its normal size.