Berlin's old airport.

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

A spherical "micro-nation" in the heart of Vienna.

Baroque celebration of the end of the Great Plague of Vienna.

Op-art architecture designed for happiness.

The crypt of the imposing Stephensdom holds royal intestines and thousands of skeletons.

The final resting place for the remains of 143 Habsburg royalty.

The Habsburgs' royal collections of art and wonders.

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

Installed in an act of one-upsmanship, the annual sundial in this church is also a symbolic victory for the Gregorian calendar.

Small on the outside, big on the inside, this church is an astonishing act of visual deception.

Legacy of the earthquake that nearly wiped Lisbon off the face of the Earth.

A king's pet, a pope's gift, an artist's inspiration, and a tragic shipwreck.

Elaborate tile work in this railway station tells the story of Portugal.

There has been an astronomical clock on this spot since the 14th century.

What happens when you cross a mayor and a painter?

What once sat in the world’s spotlight is today a largely disused ghost complex.

Where the lovelorn find a home for their sentimental keepsakes.

This fairytale castle was built as a show of power but was nearly torn down thanks to its history of torture.

This city square is home to Amsterdam's oldest church and a statue honoring Dutch sex workers.

This man-made mound monument was built out of soil from all across the Polish empire.

Poland's oldest surviving university building holds a wealth of historic science instruments including some used by Copernicus.

Real bones which are said to have belonged to a Polish dragon.

An underground city of salt.