The former private quarters and office of Dr. Sigmund Freud now hosts a museum housing the works of the founding father of psychoanalysis.

Vienna's underworld of tunnels and subterranean rivers made an iconic appearance in a 1949 Orson Welles film.

The crypt of the imposing Stephensdom holds royal intestines and thousands of skeletons.

A tiny church on a man-made island in the Adriatic.

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

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

Destroyed Serbian army headquarters sits half crumbled in a largely revitalized Belgrade.

A Serbian church lit by chandeliers made of weapons.

A pair of connected skyscrapers form this symbolic gateway.

Museum dedicated to the terror regimes of Hungary.

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

A trail of iron footwear stands as a monument to the thousands executed along this riverbank during WWII.

This statue of a falling man commemorates a teenage martyr of the Hungarian Revolution.

A series of caves under Castle Hill that once held the prisoner Vlad Tepes, better known as Count Dracula.

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

This spaceship sculpture in the middle of the Slovakian capital looks like it just crash-landed.

The former Nazi concentration camp stands as a museum to remember this dark chapter in European history.

An underground city of salt.

This Polish cave has housed a dragon, a brothel, and an enduring legend.

Real bones which are said to have belonged to a Polish dragon.

Poland's oldest surviving university building holds a wealth of historic science instruments including some used by Copernicus.

Beneath Kraków Old Town's main square lies a hologram-filled medieval market vampire graveyard wonderland.

This Nazi ruin was the site where Hitler was almost blown up by a suitcase bomb.

Once a giant gingerbread factory, this space now hosts exhibits and workshops on the historic treat.