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.

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

Op-art architecture designed for happiness.

A small museum filled with over 1,000 clocks, and one particular clock calibrated to run until the year 9999.

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

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

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

The topiary maze at the Habsburg hunting lodge.

This former insane asylum now holds a pathological anatomy museum.

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

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