One of the most extreme deserts in the world, these snow-free valleys harbor life, despite the hostile environment.

This tiny Bulgarian town offers a stunning location in the mountains and a storied history.

A fantastical group of cliffside stairways, bridges, and twisting paths carved out of stone provide a surreal coastal hike.

This giant boulder is pinched over a 1000-meter abyss by two mountains.

This everlasting lightning storm may be the world's largest generator of ozone.

This "dead marsh" sits among the largest sand dunes in the world, a forest frozen in time.

An exquisite tunnel of cascading flowers.

Bring your hiking shoes, wool socks, and thermal underwear for a stay in these cozy forest huts.

The red crab exhibits one of the most spectacular migrations on earth, despite manmade obstacles.

Reputedly haunted sandstone necropolis with exquisite stone carvings.

Mysterious spherical rocks in the semi-desert of western Kazakhstan.

Splashes of blue in an otherwise monotonous lunar landscape.

This complex of vertically-excavated Buddhist, Jain, and Hindu monolithic temples in India's Maharashtra providence illustrates a spirit of tolerance characteristic of ancient India.

An abandoned whaling station on an active volcano offers hot springs in Antarctica, surrounded by ruined giants of industry.

One of the oldest living oak trees in the Southeast.

A remarkable geological formation resembling a forest made of stone.

A tunnel dug through the side of a mountain by hand provides convenient yet death-defying access to a small village in China.

A salt lake dotted with steaming limestone chimneys.

Iceland's largest lagoon is home to stunning multi-colored icebergs.

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

Castle and secret tunnel withstood a siege until its owner was killed by the Holy Roman Empire, while sitting on the toilet.

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

Snow-capped peaks, colorful waterfalls and stunning vistas on the edge of the Himalayas.

Naturally protected city carved from a rock face.