South Korea's love of the silly photograph is on full display at this goofy collection of trompe l'oeil paintings.

Three connected pink triangles memorialize persecuted gays and lesbians throughout history.

This unattributed sculpture in Amsterdam is hiding in plain sight.

A Portuguese Jewish cemetery filled with stunning grave monuments that date back to 1614.

Famed for its pie, this eatery has a hidden tunnel that allowed Catholics to secretly walk to church during the Reformation.

A beautifully eclectic mix of architectural styles.

An ancient passage filled with stalls selling used books, once frequented by Vincent Van Gogh.

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

Cat art as far as the eye can see.

Museum preserving torture methods from the past.

A floating cat sanctuary on an Amsterdam canal.

This German bone house contains the remains of some 20,000 souls.

Twisted buildings adorn the banks of the Rhine river.

This centuries-old gothic monster has been converted into a sprawling, glossy bookstore.

This historical Netherlands fortress still bears the marks of its single siege.

While you wait to cross the street at a traffic light in Mainz, you might notice that the light is staring back at you.

A Belgian self-built tower inspired by the Bible and ancient civilizations.

This tremendous timepiece was once the largest cuckoo clock in the world.

A once-magnificent collegiate church is falling into ruin.

This strange building looks like a medieval fortress crashed into a 1960s Brutalist office block.

Descend into the tunnels to experience the life of a coal miner.

A beautiful maze marks where three countries meet.

This bakery and museum offers tours of the tastes and mythology of Aachen's signature spice biscuit—just don't ask for the recipe.

A fantastical bed and breakfast with magically unique rooms.