This skeleton-filled altar piece served as a backdrop to one of the most iconic scenes in "The Sound of Music."

The shell of a medieval fortress offers commanding views of the area it once protected.

The world's oldest known salt mine.

Vienna's underworld of tunnels and subterranean rivers made an iconic appearance in a 1949 Orson Welles film.

The personal charnel house of Anton Bruckner.

Ugly 18th-century dwarf statues living in a perfectly landscaped Austrian garden.

Double spiral staircases are not unheard of, but they are very rare.

A centuries old castle atop a dormant volcano houses museums devoted to both women and witches.

The largest ice cave in the world is thought to be the entrance to hell according to Austrian legend.

An Austrian house of bones filled with hundreds of intricately painted skulls.

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

Swarovski's museum/theme park is a fake diamond fantasia overlooked by a giant.

Terrifically morbid cemetary and site of famous Paracelsus' grave.

A three-shelf library serves as a memorial in the Jewish cemetery of Krems.

A sculpture serving as an homage to Pope John Paul II.

An alchemist's "magic door" stands in the middle of a Roman park.

This outsider art house has gone from clinical creation to astounding artwork.

Artfully arranged bones of 5,800 Austrians.

This network of conjoined cellars was riddled with traps and supposedly allowed the townspeople to pretend their homes were deserted.

This homeless brass fox tugs at your heartstrings from the foot of a Stockholm bridge.

Now a hotel, this former bank was the site of a robbery that spawned a psychological phenomenon.

Sweden's "good old days" painstakingly re-created in a model village.

Sweden's first nuclear reactor, R1, can be visited 25 meters underground.

An illuminated manuscript comprising the life's work of a lone monk, inexplicably decorated with a portrait of Satan himself.