This impressively complicated radioastronomy research center was once a tool of Soviet spies.

A plaque marks the spot where the saint was shoved off the Charles Bridge and into the river.

Macabre astrological automaton clock dating to the late 1400s.

A monument to the three wars that led to German unification towers within a Berlin traffic circle.

Thousands of coffin-like pillars make up this controversial Holocaust memorial.

Striking occult iconography on a medieval German church.

An extraordinary mechanical calculator designed by the mathematician and philosopher Gottfried Leibniz.

A spitting ode to a German serial killer.

Eight naturally mummified bodies in glass coffins are housed in an underground crypt.

A hidden church in a hidden courtyard tells the story of the Miracle of Amsterdam.

Amsterdam's former hotspot for public executions and dissections.

A Dutch passageway's artistic, aquatic-themed makeover pays tribute to the capital city's famed waterways.

A beautifully eclectic mix of architectural styles.

Museum preserving torture methods from the past.

Climb inside an iron crystal magnified 165 billion times its normal size.

A surreal statue honoring Prague's favorite literary son.

A turn of the century building boasting some of the most beautiful art nouveau architecture in Prague.

Looming communist pillar with a Czech twist.

Naturally formed rock city in Poland.

The walls and ceiling of this Polish church are decorated with thousands of skulls, with another 21,000 skeletons just below.

This fairytale medieval church in Poland originally spent centuries in Norway.

A mysterious structure left behind on the Polish mountainside, sometimes called "Hitler's Stonehenge".

This mysterious and once-grand memorial still embodies a remarkable architectural vision.

An artificial date palm stands as a memorial to Warsaw's Jewish community.