Someone loved this song enough to carve all of its lyrics onto a tree trunk in a Berlin park.

What started as a tongue-in-cheek shrine is now a full-blown museum celebrating "The Hoff" and his longtime love affair with Berlin.

A whimsical and twisted animatronic monster tour beneath the streets of Berlin.

A fascinating insight into daily life in the Eastern Bloc.

The former 1920s mansion of a prominent Catalan developer was used as the Soviet Embassy during the Spanish Civil War, and there is still a bunker below the garden.

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

A once-secret library of Freemason history in Catalonia.

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

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

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

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

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.

This 1920s Amsterdam neighborhood was built as a giant experiment in concrete construction.

The former home of a mad diplomat is said to still be marked in bloody, arcane scrawls.

The world's oldest Jewish library was founded by Sephardic Jews in 17th century Amsterdam.

This impressive collection of rare books on ancient mysticism inspired author Dan Brown.

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

The world's only museum devoted to the wonders of fluorescence.

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

A curious collection dedicated to human and animal anatomy and pathology.

Half-eaten food on display at an English café.

This antique prison is a tourist attraction with a sordid past.

The world's largest collection of witchcraft regalia.