A church of bones, decorated with 40,000 human skeletons.

A mocking tribute to the past and modern leadership of Prague.

Macabre astrological automaton clock dating to the late 1400s.

Two stunning 17th-century libraries and a cabinet of curiosities.

The gorgeous library at Trinity College is home to remarkable treasures of Irish identity.

The modern birthplace of Irish freedom.

Amidst the bustling streets of Dublin, there is a hushed garden that is dedicated to "All those who gave their lives in the cause of Irish Freedom."

This courtly monument celebrates an influential comedian who turned taking the piss out of the powers-that-be into an art.

Thanks to modern navigational tools we now know that the true prime meridian runs through a park next door.

A 1,215-foot tunnel transports pedestrians beneath the River Thames.

This one has sailed five times as far as Sir Francis Drake's famous ship.

Hear the quietest sound from across the dome.

This unattributed sculpture in Amsterdam is hiding in plain sight.

This unique Renaissance castle was turned into a home for Nazi occultism.

This proud Teutonic warrior rises out of a German forest heralding a victory and measuring lightning.

Largest illuminated advertisement sign in the world.

This "floating railway" is one of the world's oldest monorail systems.

The largest bell in the world has been swinging high above a Cologne cathedral for almost a century.

Thousands of tourists and residents in Cologne affix "love padlocks" on the Hohenzollernbrücke Bridge to symbolize their affections.

On the Spree bank, discover one of the last reminders of a symbolic wall that divided, and was torn down by the people.

An eerie, derelict amusement park in Berlin.

Berlin's old airport.

Metro station with a claim to rock n' roll fame.

A tree-like building perches on its trunk in the Steglitz neighborhood of Berlin.