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

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

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

This Budapest bar allows drinkers to leave their mark on the walls, floor, and even ceiling.

One of the most poignant ruins of the Chornobyl nuclear disaster, the local football team's stadium has been quickly reclaimed by nature.

This attraction was abandoned after the Chornobyl disaster.

The ghost town left by the worst nuclear disaster of all time is being taken over by nature and urban explorers.

This derelict superstructure was a very important warning system for the Soviet military.

A reconstructed medieval gateway that was the magnificent entrance to the capital city dating back to 1037.

The haunting complex honors the millions of Ukrainians who died in the forced famine under Soviet rule.

Last remaining nuclear missile base in Ukraine.

This abandoned Soviet circus is slowly being restored to its Communist-era glory.

A forgotten remnant of the Soviet Union, Transnistria is an unrecognized country hidden behind a heavily militarized border between Moldova and Ukraine.

This memorial to the victims of the Romanian Revolution of 1989 is often compared to a potato on a skewer.

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

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

A mountain pass in Bulgaria's Balkan Mountains was the site of four historic battles.

A magnificent, glittering building tucked into a tiny Bulgarian mountain town.

This once-grandiose behemoth of a monument from the socialist era now sits quiet and closed up.

A striking symbol of the Bulgarian capital.

A Bulgarian monument to Russia's role in World War II is constantly being painted in pop culture protest.

An abandoned saucer-shaped monument in the Bulgarian mountains.

An abandoned Byzantine fortress and notorious prison.

A whimsical bridge adorned with decorative dragons.