This abandoned Brutalist treehouse is a hidden architectural relic.

One of the largest caves in the world open to the public.

This Tuscan lake hides a 13th century town that is still visible when the water recedes.

Gigantic mosaic sculptures of the figures on Tarot cards fill this colorful Tuscan garden.

The Sighignola summit on the Swiss border offers views so breathtaking it's been named one of the most beautiful places in Italy.

This museum is rotten with a century of wax medical deformities.

The astonishing collection of an infamous criminologist.

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

This real life asylum of horrors is now an abandoned ruin that hides the unbreakable code to one patient's insanity.

This private skyway is filled with art and was expanded explicitly so that Hitler could appreciate a river.

The remains of a town so thoroughly destroyed by French forces that the citizens simply left.

This ancient Roman prison is decorated with an upside-down cross not as blasphemy but as saintly tribute.

Where Aleister Crowley taught magick in "La Chambre Des Cauchemars," his "Chamber of Nightmares."

A fairytale island floats in the middle of Italy's little-known Lake Orta.

The martyr's wax-enhanced skeletal remains lie preserved in a glass case in the Santa Maria della Vittoria in Rome.

This medieval Italian town is a sheer (and beautiful) cliffside defense.

The plague quarantine island home to the alleged "Vampire of Venice."

A complex, nine-layer maze on the grounds of a Venetian doge's playground.

The location of the last witch trials of Italy, known as "The Salem of Europe."

This sword isn't waiting for a king to pull it out. It was placed there by a saint.

Filled with goldfish swimming in a shallow pool of sea water, this ancient crypt is more wishing well than burial site.

This domed temple was built in a hidden cave mouth as a refuge for sinners seeking absolution.

One of several skulls claiming to belong to the beheaded St. John the Baptist is on display at this Roman church.

Abandoned medieval hill town.