(CNN) — It took four years of preparation and seven visits to Norway, but Czech rock climber Adam Ondra has finally completed what is thought to be the hardest climb in the world.

The 24-year-old achieved the 45-meter ascent at Hanshelleren cave in Flatanger in just 20 minutes on Monday. Ondra believes the climb to be the first that can be classified as a "9c" -- which would make it the world's hardest single rope-length climb.

"At the end of the route when I knew I did it, I had one of the strangest emotions ever," he says.

"I clipped the anchor and I could not even scream. All I could do was just hang in the rope, feeling tears in my eyes. It was too much joy, relief and excitement all mixed together."

'Project hard'

Adam Ondra completing what is thought to the world's first 9c grade climb. Courtesy Pavel Blazek

He attached bolts along the route back in 2013 and traveled back and forth to the Norwegian granite cave while edging closer and closer to his goal, dubbing his challenge "Project Hard."

"Months and months of my life summed up in 20 minutes. So much time and effort in something so short but intense as hell," he added.

"Every minute spent in Norway, every move in the gym was totally worth it. This route never really turned into a nightmare, despite the time I spent on the route. It was a fun process, and it was even more fun to finish it off."

Hanshelleren cave is a favorite with seasoned climbers, partly due to its giant overhang, which means it rarely rains inside (although water can sometimes seep through).

Located about a three-hour drive north of Trondheim, it's known for its difficult climbing routes, with grades starting from 5.0.

Ondra has previously described Hanshelleren as one of his "favorite spots" and even set the record for the world's first 9b+, the present hardest climbing grade (using a French numerical system), at the same site last year with a climb titled "Change."

Climbing prodigy

The world champion set his sights on climbing the "world's hardest climb" back in 2014. Courtesy Pavel Blazek

His last triumph was becoming only the third man ever to climb El Capitan's Dawn Wall, the fabled rock in Yosemite National Park. The world champion, who was born in Brno in 1993, climbed his first 9a at the age 13 and went on to became the first climber in history to win both the Lead and Bouldering World Cup titles.

"There are way more powerful climbers compared to me but I think I can really take advantage of all my power due to my technique," he told CNN's Human To Hero series in 2015. "Also, due to my mental strengths I can really reduce all the fear and doubts -- I can be driven by this intuition and experience, and that's when I definitely feel I climb at my limits."

His next victory may well be an Olympic medal.