The highest dunes in California are the most likely place in the area to hear the Singing Sands.

A hard-to-reach oasis in a desolate corner of Death Valley National Park.

A sulfuric martian landscape that looks far better than it smells.

Twelve sculptures designed to make their best showing with the coming or going of the sun.

A valley of unique erosion patterns lends to a view like nothing on Earth.

Massive sinkholes on a mountain in one of the most remote places in Venezuela.

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

The cinder cone volcano with a less than complimentary name.

A salt lake dotted with steaming limestone chimneys.

A remarkable geological formation resembling a forest made of stone.

An artificial crater field that trained astronauts for lunar exploration.

Splashes of blue in an otherwise monotonous lunar landscape.

Eons ago, a rushing lava river formed this pristine passage through solid rock.

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

Lunar landscape, a mud volcano and bizarre rock formations.

Mysterious hillside with a continuously burning natural fire.

The subtle interplay of fire and water is hard to ignore at this remote Jamaican spring.

A fiery-red region of scooped out land still largely untouched by civilization, tourists or otherwise.

Think you have a tough job? Try carrying 200 kilos through a cloud of sulfur down the side of a volcano.

A breathtaking canyon offers stunning views and frightful pathways through an ecological paradise.

This peculiar lake of pitch is so thick and viscous that one can walk on its surface.

An arresting arch punched straight through a mountain provides one of the most scenic spots, and challenging climbs, on the planet.

In a long-dry lake bed, these groups of massive stone pillars bear a striking resemblance to clumps of everyone's favorite fungi.

Deadly scalding and one of the largest hot springs in the world.