This eye-popping Icelandic crater lake is surrounded by red volcanic rock.

This fantastical waterfall is hidden in a cave located in a cracked cliff.

The unique waterfall in Iceland's south features a backdrop of geometric black lava columns.

Medicinal spa created with the discharge from a geothermal energy plant.

Village situated on a narrow volcanic escarpment.

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

The colorful soil of Iran’s "Rainbow Island" attracts artists and nature lovers.

The Pope’s secret escape route.

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

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

Crushed coral and crystals give the sand its signature coloration.

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

Pilgrimage site for star-crossed lovers.

Skulls from the plague of 1656 and World War II bombings are united by a cult dedicated to caring for the ancient dead.

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

Over 50 exquisite hand-painted Renaissance maps decorate a Medici storage room.

A labyrinth of ancient tunnels hidden below the city holds the ruins of 2,500 years of history.

Five candy-colored villages on the Italian Riviera.

An Italian hillside ghost town.

This quaint Italian town keeps losing ground as the sides of its plateau slowly erode.

Architectural monsters are devouring this palace's every door and window.

An ossuary built in 1210 to collect bones from the Ospedale Maggiore of Milan.

The engineering wonder and pleasure dome of a much-maligned emperor still holds undiscovered secrets.

Hidden in an Italian forest is a completely homemade amusement park that has taken a lifetime to create.