Apartment complexes built into huge repurposed natural gas tanks.

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

This museum promotes informed contraception by documenting its often secret past.

Op-art architecture designed for happiness.

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

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

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.

This former insane asylum now holds a pathological anatomy museum.

Venice's "Island of the Mad."

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

An eclectic art form practiced by untrained masters is celebrated at this museum in the heart of Zagreb's old Upper Town.

This former estate of a fascist leader is now a burnt out ruin leading to a system of secret tunnels.

Once a state-of-the-art tuberculosis treatment spa, these ruins are now ruled by paintball players.

Where the lovelorn find a home for their sentimental keepsakes.

The only museum with its curator—and her pets—buried inside.

This palatial spiral staircase was so unusual the name "snail" was given to the noble family who built it.

A new sculpture calls attention to climate change in the centuries-old city it threatens.

This community on a small Venetian island has taken to painting their houses in bright neon hues.