An Italian hillside ghost town.

Ethiopia's "smoking mountain" is in one of the hottest regions on the planet and is home to two lava lakes.

Tubing through a cave lit with glowworms is a magical underground experience.

An alien landscape of chalk-rock in the Egyptian desert.

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

One of the most spectacular canyons in the world.

Ottoman-era houses lovingly preserved.

In this historic region, homes and churches are carved into ancient volcanic rock formations.

A clear example of the process of erosion in action.

Granite rocks that concentrate waves into powerful jets.

Not one, not two, but three natural bridges remain in this captivating spot post-sinkhole.

Bohemian paradise covered in majestic forests.

Labor provided by Great Depression-era programs restored these 25,000 acres in Tennessee.

One man's extraordinary topiary garden in a small South Carolina town.

The world's brightest bioluminescent bay.

270 million year-old forest of stone.

Once connected to the outside world by a single train track, this ghost town is looked after by the National Park Service.

Canyon walls shrouded in ferns.

Major tourist destination known for its bubbling mud-pools and hot thermal springs.

Stroll through a wonderland of stupendous moss-covered trees.

Perfectly preserved ancient monastery in an impossibly dramatic location on a rocky island in the Atlantic.

Massive rock sculptures formed during the time of the dinosaurs still stand undisturbed.

An ancient stone fortress considered by many to be the eighth wonder of the world.

World's largest cave was only discovered in 1991, and now offers tours to the public.