Once the most densely populated place in the world, this island is now a ghost town.

Curious cave that stays a cool 56 degrees all year long.

Mother Nature outdoes herself with this stunningly beautiful set of caves carved into marble.

One of the deepest blue holes in the world.

The glowing blue Nymphaeum of Emperor Tiberius.

Despite being a perfectly pleasant place to be, Loyalton can't seem to attract any visitors.

An abandoned stretch of highway, deteriorating next to the operational one.

An Italian crevasse filled with abandoned buildings gives visitors a look at the world without humans.

A tropical paradise just a short trip from the opera house is filled with beautiful winged creatures.

Legends surround an ancient tree trunk riddled with nails for good luck.

Only two of these trees remain in the natural world, found high in the cloud forest of the island of Mauritius.

This small group of sand dunes manages to pack in a strange rainbow of colors.

A massive volcanic plug is now a protected area that hosts a number of bird species.

A fiery crater has been burning in the Karakum Desert since 1971.

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

St. Mary's Asylum was isolated and abandoned before being converted into a Bed and Breakfast.

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

For those with no fear of heights: a skywalk 4,700 feet up on a Chinese mountain.

A total of 999 stairs lead visitors through a massive hole in a mountain known as the Gateway to Heaven.

A subterranean ice warehouse that has lain hidden beneath central London for over a century is now open to the public.

A Spanish town built into the cliffs.

Cliffside houses provide a spectacular view from their perch above the valley.

Hot springs monkey spa in the middle of Hell's Valley.

The once highest point in China blends symbolic design with a kick of adrenaline.