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

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

Thousands of rusting train cars have been slowly falling apart on the edge of Greece's second largest city.

Bizarrely shaped rock formations in northwest Bulgaria come with equally bizarre legends.

An abandoned saucer-shaped monument in the Bulgarian mountains.

A vast Communist-era exhibition space in the Bulgarian capital.

"Holy Wisdom" overlooks the city that became its namesake.

A celebration of all things tacky, garish, and bizarrely creative in the Romanian capital.

Romania's triumphal arch looks out over Bucharest.

Something's watching you.

No one knows who built this strange cave of worship or exactly why.

A giant portrait of an ancient king looms over the river.

A countryside Romanian cemetery filled with colorful crosses bearing lyrical, ironic, or satirical rhymes.

This fairy-tale castle would make Dracula (who is said to have been imprisoned there) jealous.

The Slovenian architect designed many landmarks in the capital city, including his own dream house.

A sanctuary for sickly, stray, or wounded donkeys.

Unchanged for centuries, this medieval library keeps its books in chains.

A miniature city, once ruled by the Queen of the Netherlands.

These slanted cubic abodes are a creative if odd solution to a zoning pickle.

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

Birthplace of the "Cat in the Cradle" and a cluster of iconic, original windmills that let the Dutch tame the seas.

Hidden within a Netherlands crater is a stone bed that lets those who lie in it see the sky as a curved surface.

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

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