into the Black Hole of Calcutta, Blue Mountains, Australia Photograph by Carsten Peter, National Geographic "It feels like being swallowed by the Earth," says photographer Carsten Peter of the first of three rappels into the Black Hole of Calcutta in Claustral Canyon, located in Australia's Blue Mountains. Experienced canyoneers avoid it after heavy rains. "The immense power of the maelstrom is responsible for the wide, rounded shape. I liked the transition from dim daylight (ferns on top) into the darkness." Getting the Shot Leave it to adventure photographer Casten Peter , who specializes in erupting volcanoes, crystal caves, and any dangerous locale he can find, to take a couple risks to get this shot. "My assistant John Robens had to swim with a strobe light below the climber in a deep basin within the spray and the noise of the waterfall," recalls Peter. "He could not hear through Walkie-Talkies, nor by shouting. He was freezing in the cold water. I was on a slippery ledge on top of the waterfall, unsecured," says Peter. "We ended up with a lot of failures, but finally we shed some light into the darkness." Learn more about the daring Aussies who use ropes but no GPS to explore the Blue Mountains in " Australia's Slot Canyons ," by Mark Jenkins, in the October 2011 issue of National Geographic . Surfing the Mentawai Islands, Indonesia Photograph by Jason Kenworthy, A-Frame "I was just hugging the face of the wave waiting for it to barrel," says