Paul passed this link along to me. I've hiked to Marble Falls, an easy day hike, and this same stream runs through the Lodgpole area of Sequoia Park, but other places are pretty extreme and unaccessible.

From National Geographic's Extreme Photo of the Week

Quote:
First Descent of Marble Fork Gorge, Sequoia National Park, California

Photograph by Jared Johnson

"The rivers of California's Sierra Nevada are to kayakers what the big walls of Yosemite are to climbers," says expedition kayaker Ben Stookesberry. "And Marble Fork Gorge was one of the great unfinished puzzles." Located on the Kaweah River in California's Sequoia National Park, the 2,000-foot-deep canyon's walls are sheer and often overhanging for a thousand feet—making an exit impossible.

To solve the puzzle...