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

Hike, bike or climb? In Three Sisters Park, you don't have to choose