Around 100,000 bodies are buried below the medieval headstones, many of which mark graves with multiple bodies stacked up to 12 deep.

Macabre astrological automaton clock dating to the late 1400s.

The slender brass strip in Prague's Old Town Square was used to tell time from 1652 to 1918.

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

An ethereal glowing blue ocean cave in Croatia.

An ancient knight and a symbol of the city's freedom.

A former bank seized as a sniper vantage point during the Bosnian War is now a secret graffiti art gallery.

Bridge that died in war and was resurected.

There's a mini version of Iguazu Falls hidden in the Balkans, and it's got a rope swing.

Museum celebrating the achievements of the Soviet space program.

Moscow's imposing monument to the Space Age.

This building holds the embalmed remains of the leader of the Bolshevik Revolution.

Immortal combat in a Moscow museum.

Dr. Strangelove-esque tours reveal the inside a bunker once reserved for Stalin himself.

The gorgeous entrances into the city's underbelly look more like grand halls than subway stops.

Moscow's other, lesser known kremlin is a fairytale-like cultural complex modeled after Old Russia.

A striking symbol of the Bulgarian capital.

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

This ancient structure is widely thought to be the oldest intact pyramid in the world.

The only quarter of the Old City not dedicated to a major world religion.

This family tattoo parlor has been inking religious pilgrims in the Middle East for 700 years.

A "miracle" that seems to produce more holy fistfights than holy revelations.

This enormous sports car themed amusement park is home to the world’s fastest roller coaster.

Whitewashed mosque contains the world's largest carpet.