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

A 1,000-year-old church holds the bones of the Christian martyrs who died hiding inside it.

Late at night, the bust of the "Dracula" actor was snuck onto the facade of this Budapest castle.

An abandoned monument remembering the "Pančevo Holocaust" now stands as a shadow of its former self.

A collection of items from a way of life that no longer exists.

The Avenue of Mausolea is a series of grand palatial tombs.

A garden in Lisbon filled with giant porcelain creatures.

The world's oldest bookshop still in operation.

Legacy of the earthquake that nearly wiped Lisbon off the face of the Earth.

This Industrial Age architectural and engineering gem helps visitors and residents alike traverse Lisbon, “The City of Seven Hills.”

"Portugal's Stonehenge" is made up of nut-like stones aligned with the heavens.

Located in the thermoelectric factory that once powered the entire city, this Portuguese museum is shockingly fascinating.

Hidden beneath the streets of London is a secret subway that only carried mail.

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

The sign at the garden gate reads: "These Plants Can Kill."

The mysterious, fantastical woodland inspiration for "The Lord of the Rings."

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

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

A subterranean Holocaust refuge within one of the world's longest cave systems.

The largest catacomb system in the world.

A nearly 500-year-old sculpture depicts a man eating a sack of babies, and no one is sure why.

The bizarre visions of H.R. Giger, tucked away in a Swiss medieval city.

This amazing pedestrian suspension bridge in the Swiss Alps would give Indiana Jones nightmares.

Large Hadron Collider and the Birthplace of World Wide Web.