The tunnel's elegant proportions keep you snug with no claustrophobia freak-out.

This tipsy office building in downtown Prague was originally called “Fred and Ginger.”

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

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

Isaac Newton's former home, where the famous apple tree still stands.

This charming railway is one of the oldest and steepest funiculars in England.

This bridge is the first to be made entirely from iron, but designed like it was still made of wood.

The house that took a plunge into the facade of a museum.

Apartment complexes built into huge repurposed natural gas tanks.

Giant WWII fortresses that fired 8,000 rounds a minute, now home to thousands of pigeons.

Beautiful Austrian natural history museum with carved ceilings and row after row of ancient taxidermy.

Op-art architecture designed for happiness.

Built to give thanks for the passing of a plague epidemic, this cathedral is a one-of-a-kind architectural hybrid.

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

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

Cold war icon and onetime "hole" in the iron curtain.

Berlin's old airport.

The bunker where Hitler took his own life is hidden under this deliberately ordinary parking lot.

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

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

A museum dedicated to the history of a terrifying secret police is now held in their former headquarters.

The most visited, and possibly most controversial, museum in Germany.

A maze of crosses marks the jumbled divide between the Netherlands and Belgium.

The site where one of the most famous poems of World War I was composed is preserved to honor the legacy of the work.