Vienna's giant wonder wheel had a starring role in one of the greatest noir movies of all time.

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

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

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

The Habsburgs' royal collections of art and wonders.

Collection dedicated to funeral rites, equipment, and mourning rituals of the Viennese.

This cubist Vienna church building looks like some sort of alien stonehenge.

Op-art architecture designed for happiness.

This Austrian museum celebrates the work of famous forgers and their inimitable imitations.

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

Located right outside of Vienna, visitors can take in expansive views of an ethereal forest.

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

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

The resting place for anonymous victims of the Danube's dark waters.

One of the best collections of wax anatomical models in the world.

The topiary maze at the Habsburg hunting lodge.

This South London cemetery holds the remains of more than 15,000 people.

The largest of London's subterranean rivers and once a mad, bad center of London life.

An unusual round church in London with a Templar past.

Winding paths and ramshackle mausoleums in the oldest "park cemetery" in London.

One of the few remaining casualties of the London Blitz, this destroyed church has become an enchanting public garden.

Hidden beneath the streets of London is a secret subway that only carried mail.

The music is over at the Ballhaus Riviera Ballroom, but the ballroom remains in haunting disrepair.

A state-of-the-art medical facility from the Imperial era is now a derelict ruin.