This massive underground salt mine now holds a sci-fi theme park in its depths.

This Transylvanian church has changed its denomination four times.

This gem is often wrongly overshadowed by the larger, newer Metropolis church in Athens.

Where commuters walk through remnants of an ancient Greek necropolis.

Heralded as the world's first theater, these ruins are often overlooked as they reside in the shadows of the Acropolis.

An ancient octagonal weather station named for the eight Greek gods of wind.

The Cycladic architecture makes this Athens neighborhood feel like an island paradise hidden in the shadow of the Acropolis.

The romantic garden was the epicenter of the Hungarian art scene in the 1880s.

A Parisian cemetery where the elite and artistic are interred beneath an eccentric collection of tombs.

This Parisian café sticks almost exclusively to an ethos of reuse.

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.

France's most famous cemetery, with some of its most curious tombs.

On Gellért Hill, this statue depicts the tragic tale of lovers divided by the Danube.

A 13th-century convent where St. Margaret of Hungary spent her teenage years.

The geographical center of Budapest is marked with a 10-foot-tall stylized zero.

A Trabant car, a kangaroo statue, and a plethora of plants take over this abandoned-factory-turned-bar.

Museum dedicated to the terror regimes of Hungary.

This off-beat, quirky communism-themed bar isn't afraid to poke fun at its history.

The narrowest street in Paris.

The tradition of open-air secondhand and antiquarian bookselling in Paris dates back to the Renaissance.

This bridge was constructed from the rubble of the infamous Bastille.

A surrealist timepiece by the artist of melting clocks.

Built in 1870 at the bridge that connected Buda and Pest, this spectacular incline railway was almost lost forever during World War II.

This Hungarian castle was built out of cardboard and wood until it proved so popular that it got upgraded to stone.