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

This iconic L.A. bookshop is housed in an abandoned bank—both symbolic and chic.

A peculiar mansion built by the troubled heir to the Winchester Rifle Company fortune.

This astonishingly geometric cave has inspired everyone from Jules Verne to Pink Floyd.

A psychedelic labyrinth on the San Francisco bay.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

This ornate Victorian marketplace was the setting for Diagon Alley and the Leaky Cauldron in the Harry Potter films.

A beautiful and abandoned New York subway station from 1904, complete with chandelier.

London's creepiest cemetery was once the site of dueling magicians and mobs of stake-carrying vampire hunters.

One of the most well-preserved castles in Italy also contains a rare medieval example of a port fortification.

The top of society once luxuriated in this world-class hotel, which continues to impress, even in ruin.

A cave in southern Italy adorned with thousand-year-old Biblical frescoes existed in obscurity until fairly recently.

Vast network of air raid tunnels beneath Lombardy's capital.

A spiritual sanctuary in a natural cave.

An open-air museum in a mountain valley features works designed to blend in with—and disintegrate back into—their natural surroundings.

An eccentric artist's abode in this small Italian town has been transformed into a surreal temple of mosaic madness.

A madman's personal garden filled with 1,000 sculpted heads.

This entire town moved to a safe location after it was devastated by an earthquake, but the remains of the original town are still around.

A line of abandoned, alien-like fortresses dot the mountains of North Italy.

A factory director designed what was the world's longest suspension footbridge in 1923 so his employees could get to work safely.

Geometry and mystery come together in an epic show of octagonal masonry.

Crumbling ruins of the thermal baths that once attracted royals and aristocrats from throughout Europe.

The world's oldest surviving anatomical theater, where "the dead are pleased to help the living."

A fairytale-like medieval church perched atop a rocky cliff on Italy's "Coast of the Gods."