Ora Cave, Papua New Guinea Photograph by Stephen Alvarez, National GeographicThe crash of rapids surrounds expedition leader David Gill, left, and Herb Laeger near the entrance of Ora Cave. Hot acidic waters welling up from deep underground, combined with drainage from heavy rains, have carved a maze of tunnels and chambers through New Britain’s young limestone. Download Wallpaper (1600 x 1200 pixels)
Hoh Rain Forest, Olympic National Park Photograph by Wai Chee Wong, Your ShotMost people know about the Hoh Rain Forest in Olympic National Park, but only a few are lucky to discover the wonder near Sol Duc. Download Wallpaper (1600 x 1200 pixels)
Alatna River Valley, Gates of the Arctic Photograph by Michael Christopher Brown, National Geographic“I paddled across this deep, slow-moving river in my small pack raft,” says adventurer Andrew Skurka. The Alatna meanders south from the Gates of the Arctic National Park. Download Wallpaper (1600 x 1200 pixels)
Desert Rivers, Mexico Photograph by Adriana Franco, Your ShotRivers forming treelike figures on the desert of Baja California, Mexico Download Wallpaper (1600 x 1200 pixels)
Spring Stream, Finland Photograph by Kyle Ueckermann, Your ShotI took this photo at the edge of a small stream in Lehtimaki, Finland. The ice is beginning to melt, revealing the water beneath. Download Wallpaper (1600 x 1200 pixels)
Fraser Island, Australia Photograph by Peter Essick, National GeographicTannin–rich runoff from Fraser’s interior stains the sea in the aftermath of a summer storm. Download Wallpaper (1600 x 1200 pixels)
Snake River, Wyoming Photograph by Michael Melford, National GeographicSnake River Headwaters Bridger-Teton National Forest, Wyoming 387.5 miles protected since 2009 Download Wallpaper (1600 x 1200 pixels)