The second-largest Jewish temple in Bulgaria was deserted after World War II, seized by the communist government and then abandoned again.

This ancient theater, restored in the 20th century, lives on as a venue for dramatic and musical performances.

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

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

Museum dedicated to the terror regimes of Hungary.

A towering spire in the fortress of Kalemegdan honors the victorious armies of Serbia during their struggles against the Ottoman Empire.

The unusual sculptures are believed to be powerful political symbols.

At this archaeological site, visitors can explore the ruins of the capital of the former Roman province of Moesia.

A hidden stream deep in the mountains creates one of the largest tufa waterfalls in Serbia.

Imperial palace of Emperor Galerius, the Emperor behind the worst Christian persecutions during the Roman Empire.

A Roman monument to their own civil engineering prowess.

Abstract monuments express sorrow and resilience at the site of a horrific massacre in Nazi-occupied Serbia.

This 14th century castle withstood years of battle but is now sliding off the hills into the Danube.

Structure built from the skulls of vanquished foes.

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

A pair of connected skyscrapers form this symbolic gateway.

Nikola Tesla's ashes are held in a golden sphere, surrounded by his works.

A World War II evacuation tunnel turned into a history display of Croatian state and people.

This 135-year-old weather station studied the effects of the climate on human health.

One of the best-preserved Roman amphitheaters is still used today, but for less brutal events.

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

This Croatian fairytale castle is slowly falling apart thanks to years of neglect.

Where the lovelorn find a home for their sentimental keepsakes.

A chain of 16 wondrous lakes formed as a result of the gradual dissolution of soluble layers of bedrock.