Nine daredevils have gone over Niagara Falls in barrels and lived to tell the tale. This week, ice climbers Will Gadd and Sarah Huenikenbecame the first to reverse the trip.

The pair became the first to ascend the world-famous falls on Tuesday, following a 30-foot-wide (9-meter) strip of rotten spray ice that formed along the left edge of Horseshoe Falls, which rises up 150 feet (46 meters) as it straddles the border between the United States and Canada.

Horseshoe Falls is the largest of Niagara's three major sections, or cataracts, and is considered the most powerful waterfall in the world.

"It vibrates your intestines and makes you feel very, very small," said Gadd of the thunderous falls. "I've never experienced anything like it."

View Images "It vibrates your intestines and makes you feel very, very small," said Gadd of the thunderous falls. "I've never experienced anything like it." PHOTOGRAPH BY CHRISTIAN PONDELLA, RED BULL CONTENT POOL

Gadd and Hueniken, both Canadian, made the ascent on Tuesday afternoon, though news of the climb was kept secret by Red Bull, the energy drink maker, which sponsored the attempt and planned to publicize it after the Super Bowl. When word leaked out, the company released the news.

Gadd, 47, led the overhanging ice climb belayed by Hueniken, 34, who spent hours huddled in an ice cave part way up the route to avoid being hit with chunks of ice.

"The power of the falls is staggering," Gadd said after reaching the top. "It vibrates your intestines and makes you feel very, very small. I've never experienced anything like it."

The U-shaped Horseshoe Falls stretches for 2,200 feet (670 meters) from Terrapin Point on New York's Goat Island to Table Rock in Ontario. The falls drain from Lake Erie into Lake Ontario at an average rate of four million cubic feet (113,267 cubic meters) per minute. It was widely reported that the falls froze last year during the polar vortex, butNiagara Falls State Park officials say that Horseshoe Falls has never completely frozen.

The most difficult challenge of the historic ascent was not the climb itself, Gadd said after he had summitted, but rather the year-long bureaucratic process to get permission.

View Images The most difficult challenge of the historic ascent was not the climb itself, Gadd said after he had summitted, but rather the year-long bureaucratic process to get permission. PHOTOGRAPH BY CHRISTIAN PONDELLA, RED BULL CONTENT POOL

"As a kid, I always felt drawn to the edge of the falls," said Hueniken, who grew up near the falls, after the climb. "I think it's human nature to be curious about gravity and to wonder what it would feel like to go over.

"It's a weird thing, but anyone who has been to the falls knows the feeling," she said. "This place has a kind of power over people."

Gadd was reluctant to rate the climb, but when pushed he called it agrade 6, the second highest rating on the ice-climbing difficulty scale. He said the most difficult challenge of this historic first ascent was not the climb itself, but the year of red tape he had to negotiate to get a permit for the climb.

Like going over the falls in a barrel, it is illegal to climb in Niagara Falls State Park on both sides of the border, and according to Tom Watt, the park superintendent on the New York side, no one had ever bothered to ask for permission before Gadd.

Adventure Magnet

Renowned as a destination for honeymooners, Niagara Falls also has a long tradition of drawing daredevils to its edge. Annie Taylor, a 63-year-old schoolteacher, was the first person to go over the falls in a barrel back in 1901.

"No one ever ought do that again," she is reported to have said when she emerged from the barrel, battered and bleeding, at the bottom of the falls. In the 114 years since, 14 other people have repeated the stunt, five of whom died in the process. Taking the plunge over the falls is illegal, and those who survive face arrest and heavy fines.

Gadd is a professional extreme athlete (and National Geographic Adventurer of the Year) who has been pushing the boundaries of multiple sports for nearly three decades. He's won three gold medals in ice climbing at the X Games, won the Canadian national sport-climbing championship four times, won the U.S. and Canadian paragliding nationals, holds the world distance record for paragliding (263 miles [423 kilometers]), flew a paramotor across the United States, and kayaked dozens of first descents of rivers across North America.

He's also written the definitive how-to book on ice climbing, Ice and Mixed Climbing: Modern Technique, which has been translated into five languages. "He's the kind of guy who makes you feel like almost anything is doable," says Hueniken, his girlfriend and frequent climbing partner. "His biggest problem is just that he needs about ten more lives to accomplish everything that he's constantly dreaming up."

Gadd celebrates after making it to the top of the falls.

View Images Gadd celebrates after making it to the top of the falls. PHOTOGRAPH BY CHRISTIAN PONDELLA, RED BULL CONTENT POOL

Watt, the park superintendent on the New York side, was initially reluctant to consider Gadd's request for a permit to climb the falls.

"I had to be cordial, but in my mind I was saying 'hell, no' when Will and his team first approached me about climbing the falls," Watt said during a pre-climb interview at the Top of the Falls restaurant, which sits on Terrapin Point directly above the climb.

Falls Are "Star of the Show"

As it turned out, Gadd's timing could not have been better. His proposal crossed the desks of a few politicians in Albany not long after Governor Andrew Cuomo had pledged to pump a billion dollars over ten years into the Buffalo-Niagara region, called the "Buffalo Billion" project, to help reinvigorate the economy of upstate New York.

Watt is overseeing the biggest influx of cash in Niagara Falls State Park's history. Established in 1885, it's the oldest state park in the nation. It attracts eight to ten million visitors a year, making Niagara one of the most popular tourist attractions in North America (for comparison, Yellowstone and Yosemite National Parks see approximately four million visitors per year).

Among the projects that are now under way to revamp the park, the most ambitious is the plan to remove the four-lane Robert Moses Parkway, which separates the park from the city, and create walking and cycling trails that will serve as greenways directly connecting the park to the city.

Because of the Buffalo Billion project, Watt said he was "encouraged" to consider Gadd's proposal. He did and soon realized the climb was an opportunity for the park to highlight the beauty of Niagara Falls in winter, a time when the park traditionally sees very few visitors.

"Not to take anything away from Will, but in my opinion the star of this show is the falls," Watt said. "For me the emphasis should be less about the act of climbing and more about the sheer beauty and power of the falls … Now we'll get to share the view that Will had during his climb."

Rigging Frozen Falls

Gadd brought me in on the project to serve as one of his riggers and to be in charge of scene safety at the base of the climb. The staging area was on an exposed mound of ice just to the left of the falls, beneath a limestone wall festooned with a camera crew and precariously perched mushrooms of spray ice.

To reach the start of the route, Gadd had to traverse a mushy slope of ice directly above a rumbling pit of churning rapids hemmed in by house-size blocks that looked like icebergs. Gadd jokingly referred to the pit as the "Cauldron of Doom," but his safety plan dictated that we install an anchor where we'd tie the end of a 200-foot (61-meter) rope with a life ring on the end.

As I built the rig with the assistance of Lieutenant Patrick Moriarty, a 30-year veteran of the New York State Park Police and co-team leader of the park's rescue team, we took one look into the cauldron and quickly agreed that if anyone fell in, they were on their own.

Moriarty, 58, has been the first responder on countless rescues and body recoveries over the years, including a dramatically close call in March 2012 involving a distraught gambler who decided to take a ride over the falls, sans barrel.

"I just hope that when people see the photos and video of Will climbing the falls that they understand that he is a true professional and that this isn't something amateurs should be doing," said Moriarty as he watched Gadd top out in almost the exact spot where the rescue had taken place. "I do worry that the wrong type of person might decide that they're going to try it."

Moriarty is usually the one who has to pick up the pieces when people make bad decisions in the park.

Hueniken was cold and stiff when she finally emerged from the ice cave to follow Gadd's lead and remove the ice screws he placed on the ascent for protection. Hanging from one ice tool, she windmilled her other arm, trying to get some blood back into her frozen fingertips. When she pulled over the lip 45 minutes later, her father stood on the Canadian side of the river beaming with pride.

She grew up 20 miles (32 kilometers) from Niagara Falls, and as a child it had been a family tradition to visit the gorge on Father's Day. "I think this might mean more to me than it would for someone else because I grew up near here," Hueniken said after completing the climb.

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