This scale model of our solar system hid in plain sight for years before a physics team sought out all the planets.

A beautiful mountaintop mausoleum devoted to a Montenegrin icon can't seem to make everyone happy.

A sharp sculpture made of thousands of pieces of jagged glass.

Seventeen oak trees sprout from the roof and walls of this tiny chapel without any visual evidence of roots.

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

This quaint Hungarian railway system is operated exclusively by children between the ages of 10 and 14.

A museum dedicated to a secret military hospital hidden beneath a castle in Budapest.

Possibly the world's largest hourglass only needs to be reset every New Year's Eve.

A museum in the childhood house of a medical pioneer.

From Austrians to Nazis to Soviets, this historic Budapest fortress has a history as complex as the city itself.

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

Museum dedicated to the terror regimes of Hungary.

A sinuous path among steep cliffs creates a stunning sight in southwestern Serbia.

Now abandoned, the world's first torpedo factory is crumbling into the sea.

Island wonderland for communist autocrats.

The only gulag ever to exist in socialist Yugoslavia.

Longest fortress system anywhere in Europe.

A wonderfully strange collection of 500+ stuffed frogs doing people things.

Where the lovelorn find a home for their sentimental keepsakes.

These historic defenses ensured the city within would survive hundreds of years of occupations, sieges, and invasions.

This cluster of little wooden huts once ground local farmers’ wheat into flour during the days of the Austro-Hungarian Empire.

A curious cave church carved into the face of a cliff.

Bridge that died in war and was resurected.

The romantic botanic tunnel feels like a well-kept secret.