Gusting winds whip at Eli Ellis’ mane of brown hair as he splays his arms wide, balancing on a 0.8-inch strip of webbing. Four hundred fifty feet of air stand between him and the ground. The 1,100-foot-long highline, named “Thirst” (a nod to its anchors on the First and Third Flatirons), stretches between two of Boulder’s most iconic rock formations, which stand over the city like watchful sentinels.

Ellis is the first to step onto the line, tethered by a harness and leash for safety. The breeze rushes past his ears, sending S-shaped ripples down the webbing. Yet his heartbeat remains slow and steady. Balancing at such heights demands absolute focus – what he calls a “Zen state of mind.” His gaze locks onto the summit of the First Flatiron, more than 1,000 feet away. Then, he takes his first step off solid ground and into thin air.

An exhilarating sense of freedom swells through him. Below, Boulder bustles like a miniature city, nestled along the foothills. A red-tailed hawk weaves playfully around the highline, unfazed by its presence. As gusts gain strength, Ellis sways with the shifting line, trusting it as much as his own technique. 

Bringing this moment to life took seven years of planning, 16 people and 15 hours to climb the Flatirons, rig gear and walk the highline. For Ellis, it’s more than a personal achievement – it’s the culmination of a lifelong dream.

 

A Dream Takes Shape

Ellis grew up in Boulder with the Flatirons ever present on the horizon. He started slacklining at The Spot climbing gym as a teenager, practicing on a short line a few feet above the ground. The challenge of aligning his body with the tension of the line fascinated him. As he honed his skills, he transitioned to highlining – walking lines at least 100 feet in the air, secured with climbing-grade anchor systems and a safety leash.

While hiking Boulder’s trail network, he scouted untouched highline locations. Though the Flatirons have long been a climbing mecca, no one had crossed the dramatic gap between the First and Third. In 2018, he set his sights on being the first.

Over the years, Ellis built a career as a professional highliner, traveling the world, securing brand sponsorships and winning competitions. But the dream of walking “Thirst” remained out of reach. The Boulder Open Space and Mountain Parks Department denied permit requests in 2018 and 2019, citing concerns over the line’s proximity to popular trails and climbing routes.

Then in August 2024, Logan Henning, alpine highline pioneer and friend, proposed a solution. He drafted a comprehensive safety plan addressing common misconceptions about highlining’s risks, detailing backup systems and outlining emergency protocols. “People perceive highlining as a death wish,” Ellis said, “So they’re surprised to find out we’re not adrenaline junkies.”

Henning’s persuasive approach worked: the long-awaited permit was finally approved.

 

Highline Before the Wedding

For Ellis, the timing was surreal. The highline he had dreamed of for years would happen on Oct. 12 – just one day before his wedding to fiancée, Lauren, whom he met through slacklining in 2018.

“There were never conversations about ‘can I’ or ‘should I,’ ” Ellis said. “From the start, she told me, ‘We’ll make this happen for you.’ ”

The ceremony, held at Flagstaff House, overlooked the very Flatirons he had long dreamed of traversing. “You could probably see the highline in our wedding pictures,” he laughed. “It would have been heartbreaking not to go for it.”

Before dawn, Ellis and half of his crew climbed up the Third Flatiron, hauling 50-pound backpacks full of gear. Henning and the rest of the team ascended the First. The setup process was grueling: they spent an hour hiking up, six hours rigging the line and the entire morning securing redundant safety measures. By noon, the line was ready. 

From Chautauqua Park, Ellis’ fiancée and wedding party watched as he stepped onto the line. A third of the way across, fierce wind forced him to turn back. Although he didn’t get to “send” the line – crossing the full length without falling – he didn’t see it as a failure. “Wind is a fickle but powerful part of flying. I don’t get scared of it anymore. I just feel so alive,” Ellis said.

After celebrating atop the Flatirons, he raced down the mountain – arriving just in time for his rehearsal dinner, greeted by cheers from family and friends.

 

A Community in the Sky

Eleven people attempted “Thirst” that day, with six completing the crossing. Three made it without falling – only one was needed to officially establish and name the line. Among them was Logan Henning, the first to send it.

Henning had been terrified his first time on a highline in 2019. But his perseverance propelled him to the sport’s upper echelon. Often called the “solo highliner,” he’s notorious for hauling 100-pound packs into remote alpine environments, walking highlines alone in the vast, rugged landscapes of Rocky Mountain National Park.

For Henning, highlining is a form of prayer. “It’s the most focused prayer I could have, but without words,” he said. His next goal? Pushing highlining into the mainstream, elevating it to the level of other extreme sports.

Henning’s feats reflect the growing community of highliners pushing the limits across Colorado’s diverse landscapes. He has traversed lines strung between the towering dunes of Great Sand Dunes National Park and balanced atop the isolated sandstone pillars of Independence Monument near Fruita. He has walked with unwavering focus across lines parallel to Interstate 70 in Glenwood Canyon and between ice walls at Lake City.

Colorado’s highlining community is one of the most tightly knit in the country. Slackliners gather in Boulder’s parks, welcoming newcomers into the sport. “With a bit of balance,” Henning believes, “anyone can experience the joy of walking on a line.”

Though highlining is a relative newcomer to Colorado’s extreme sport scene, the state’s adventurous spirit is nothing new. Trailblazers like Henning and Ellis build upon Colorado’s long tradition of pioneering outdoor pursuits, using highlining as a way to explore every nook of the state’s canyons, peaks and deserts – from a birds-eye view. 

For Ellis, Colorado’s skies hold a special pull. “I’ve been highlining all over the world, but Colorado is my favorite place to be up in the sky. It’s like returning home and seeing it from a perspective you can only get from up high.”

Though his dream highline is now complete, his ambitions remain sky-high. He’s now channeling his skills into competitive ice climbing as a member of the USA Ice Climbing team. But in his free time, he can still be found slacklining with his wife in a Boulder park.

As for “Thirst,” Ellis sees it as more than an athletic feat. It’s a symbol of perseverance – on the line and in life. Because even in the most turbulent moments, balance can always be found.