Eco-village hidden in the foothills of the Alps that created a massive system of psychedelic underground temples.

This half-finished "city of toys" was almost Italy's own Las Vegas.

On rare days, this abandoned castle's gatekeepers open its doors, revealing the eye-popping splendor hidden inside.

Hidden behind a wall for decades, this masonic lodge was only rediscovered during renovations.

Pompeii's less famous neighbor is still revealing her secrets.

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

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

A small island less than half a mile from Venice is a forbidden island with a dark and twisted past.

A 16th-century horror show built in a lovely Italian garden.

Sitting on an Italian hilltop is this surreal fortress built by the mad inventor of electrohomeopathy.

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

Venice's "Island of the Mad."

The last moments of the ill-fated Pompeiians, frozen forever in plaster.

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

A collection of grotesques lines the walls of this Italian villa.