This small 16th-century church in Athens is almost entirely surrounded by a modern building.

Heralded as the world's first theater, these ruins are often overlooked as they reside in the shadows of the Acropolis.

The ruins of an ancient Roman tomb hidden in the basement of a trendy clothing store.

The Cycladic architecture makes this Athens neighborhood feel like an island paradise hidden in the shadow of the Acropolis.

This spooky statue sits outside a famous Prague theater.

The oldest cemetery of modern-day Athens blends the modern and ancient worlds.

The ruined doorway is a portal to the building's turbulent and torturous past.

An ancient octagonal weather station named for the eight Greek gods of wind.

This ancient Greek place of assembly and marketplace is being revealed layer by layer below the modern Athens cityscape.

The abandoned summer estate of the former Greek Royal Family.

This Hungarian castle was built out of cardboard and wood until it proved so popular that it got upgraded to stone.

A fake Transylvanian castle houses a cathedral of antlers.

This lurid German fountain plots the sad course of marriage from dating to death.

This abandoned coliseum was intended to be a grand Nazi rallying ground before it was halted at the end of the war.

A castle from the Holy Roman Empire that hosts traveling youth... in its stables.

2300-year-old Roman road connecting the empire.

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

A copy of the famous statue can be found in this Florence piazza, along with one of the most breathtaking views of the city below.

This private skyway is filled with art and was expanded explicitly so that Hitler could appreciate a river.

Monument to a suicide protesting the Soviet invasion.

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

Walk through Czech history in Prague's largest graveyard.

Countless grotesque faces stare out from this eerie Prague art wall.

Macabre astrological automaton clock dating to the late 1400s.