10 must-see treasures outside of Yellowstone

Did we solve the mystery of the 'sailing stones'?

Mount Roraima: 'A remote island in the sky'

How do you clean up a contaminated river?

Climbers reach for their passions in 'Meru'

Jewels of the forest: The fascinating world of tree frogs

Why these gravity-defying rocks don't fall

4 ways to start a fire (when you really need it)

Teen found alive 2 days after plane crash

3 ways to use backlighting for more creative nature photos

Wild animals fascinated by mirror left in jungle

Mystery of Greenland's 'disappearing lakes' solved