St. Mary's features one of the most spectacularly decorated cathedral interiors in all of Europe.

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

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

This attraction was abandoned after the Chernobyl disaster.

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

When you've got to go, you've got to go.

The deepest metro station in the world.

Glowing orb in Minsk houses 8,600,000 items.

Remnants of the city's Soviet history hover over this modern fast-food outlet.

A full figure 4th century incorruptible saint lies in a glass coffin in Croatia.

A wunderkammer of gold and silver reliquaries and ancient saintly bones.

The complex has been abandoned since the Croatian War of Independence, barring a stint as a set for 'Game of Thrones.'

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

A curious little museum dedicated to the furry feline in the cat haven that is Old Town Kotor.

In the hometown of the Catholic saint and Nobel Peace Prize winner, a memorial dedicated to her legacy.

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.

This communist behemoth is the heaviest building in the world and a legacy of a brutal regime.

Romania's triumphal arch looks out over Bucharest.

The true meaning behind this sculpture remains unknown.

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

A dead saint, a deadly poison, and a mysterious holy ooze.

Go inside to really appreciate this 500-year-old technological masterpiece.

Venice's "Island of the Mad."