Op-art architecture designed for happiness.

Vienna's diversity-themed traffic lights were inspired by the Eurovision Song Contest.

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

The beautiful baroque library of the Hapsburg empire.

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

Legends surround an ancient tree trunk riddled with nails for good luck.

An abandoned NSA listening post on Berlin's "Devil's Mountain."

The skeletal frame of a decommissioned gas-pumping station offers breathtaking views of greater Berlin.

An imperial church bombed to ruins during WWII now stands as a jagged memorial.

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

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.

This water-tower-turned-high-end-apartment building was once the site of an early Nazi concentration camp.

Inside this Jewish cemetery is a memorial to soldiers who deserted the German army and were executed.

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

The site of the famous Nazi book burning campaign of 1933 remembers its "Night of Shame".

A narrow passage next to a cafe leads to a courtyard exploding with murals, tags, and paste-ups.

This 1,300 year old monastery built atop a single rock was once only accessible depending on the whims of the tide.

There is a strange little carving of a person seemingly crushed by a pillar behind the remains of St. Thomas Aquinas.

This modern museum of Mediterranean culture is surrounded by a surreal concrete honeycomb.

Wander among free-roaming storks at the sanctuary that helped save them from local extinction.

The castle was reconstructed to fit Kaiser Wilhelm II's romanticized vision of the Middle Ages.

The water-powered carriages are long gone, but for over a century this funicular railway has been the fastest route to the highest point in Paris.

The vast, legendary catacombs hold secrets much stranger than stacked bones.