A base jumper leaps from the 980-foot open deck of Malaysia's Kuala Lumpur Tower. Base jumping is an extreme sport in which participants leap from fixed objects and use parachutes to slow their falls.
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People watch a surfer ride a wave off the coast of Praia do Norte near Nazare, Portugal. The fishing village features a 16,000-foot-deep underwater canyon, churning up some of the largest and most dangerous waves on the planet. Today's big-wave surfers are often towed onto massive waves by jet skis or helicopters.
Adriana Jimenez competes in the finals of the 2014 Red Bull Cliff Diving Women's World Series, held in Yucatan, Mexico. Cliff divers will often hit the water at speeds over 50 mph.
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Ice climber Will Gadd ascends Helmcken Falls at Wells Gray Provincial Park in British Columbia, Canada. The 450-foot cascade never fully freezes, but it leaves a blanket of ice on the surrounding walls. It's considered one of the world's most difficult climbs.
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Mexican kayaker Rafa Ortiz drops over the 189-foot Palouse Falls in southeast Washington. He was the second person ever to paddle over the edge. American Tyler Bradt set a world record in 2009 when he successfully kayaked the falls.
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Alain Robert, known as the "French Spider-Man," scales a 610-foot skyscraper in Paris' La Defense district. Often forgoing ropes and harnesses, Robert has established himself as one of the world's best free solo climbers. He has racked up numerous arrests and a few serious injuries along the way.
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Switzerland's Ueli Gegenschatz flies over Botafogo Bay in Rio de Janeiro. The special wingsuit he's wearing allows skydivers and base jumpers to soar through the sky with their arms spread open.
Jason Boule/Air Race Pilots Association/AP
Dean Potter walks high above the air at the Three Gossips in Utah's Arches National Park. Unlike tightrope walking, highliners must maintain their balance on a slack line instead of a taut one. Potter died in a wingsuit flying accident at Yosemite National Park on May 16, 2015.
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A motocross rider performs during a show in Ashkelon, Israel. Freestyle motocross involves high-flying stunts meant to impress judges.
Freeskier Ted Davenport soars over Mount Aspiring National Park in Wanaka, New Zealand. Speed riding, aka speed flying, combines freestyle skiing and paragliding for a fast, thrilling ride close to the slope.
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Roland Morely-Brown rides down a ridge during the 2011 World Heli Challenge at Wanaka's Mount Albert. In heli-skiing, skiers and snowboarders travel by helicopter to areas not accessible by other means.
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Freerider Kyle Strait competes in the 2014 Red Bull Rampage near Zion National Park in Virgin, Utah. Freeride mountain biking usually involves large drops, jumps and stunts.
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Cave divers explore the Orda Cave in Russia's western Urals region. Cave diving is one of the most dangerous kinds of diving or caving in the world and requires specialized equipment and training.
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Two men coast down the Cerro Negro volcano in Leon City, Nicaragua. The Cerro Negro is one of Nicaragua's most active volcanoes, and it is a popular spot for the young sport of volcano boarding, or volcano surfing.
A paraglider flies over the Oster-Jansjon lake in Are, Sweden. In the right conditions, paragliding flights can last for hours and reach thousands of feet in altitude.