Op-art architecture designed for happiness.

The former private quarters and office of Dr. Sigmund Freud now hosts a museum housing the works of the founding father of psychoanalysis.

Macabre museum devoted to historical Viennese murders.

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

A tropical paradise just a short trip from the opera house is filled with beautiful winged creatures.

The beautiful baroque library of the Hapsburg empire.

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

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

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

Bizarrely-painted church designed by a controversial artist.

The prototype for all Nazi concentration camps.

The world's most important buildings shrunk to a tiny size.

Each year melting snow turns these Austrian hiking trails into scuba zones.

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

Remarkably preserved body discovered in a peat bog.

Most prolific publishing house in the 1600s open to the public.

A miniature city, once ruled by the Queen of the Netherlands.

A former plague hospital turned medical museum.

Oldest Museum of the Netherlands is a true cabinet of curiosities.

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