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That is being the first to climb Dunedin's Baldwin St 134 times (the 8848m equivalent height of Mt Everest) and finishing without altitude sickness, frostbite or any other serious injuries.
The 52-year-old Christchurch man started the marathon journey at 9am on Wednesday as part of the Everest challenge.
The concept is simple: Pick any hill, anywhere in the world and ride a bicycle, run or walk repeats of it until you climb 8848m.
Mr Roozen said more than 3000 people around the world had completed the Everest challenge, but until today, no-one had done it on the world's steepest street.
"The Everesting community have been saying this is one of the iconic streets and asking who's going to be the first to do it.
"So I thought I'd be the first."
After every 15 hikes up the street, he stopped for food, drink and a short rest before resuming the hike.
"You're not allowed to sleep, though. That's part of the Everesting rules."
During one of his breaks yesterday, he said his body was holding up OK.
"The steps on Baldwin St are amazing. It makes it a lot easier.
"And on the parts of the street that don't have steps, I've been zig-zagging up because it puts less stress on the legs.
"People have been asking me why I'm doing that. If you're going to walk up and down here over 130 times, you have to pace yourself."
Mr Roozen said he had done nine Everest challenges on a bicycle on various hills around the country, and this was the second time he had done a walking/running Everest challenge.
Why? Because it was the closest he would get to climbing Mt Everest, he said.
He had no ambitions to actually climb the world's tallest mountain.
"I do it because it's just me. If you fail, nobody's going to worry about it. It's really a personal challenge and it keeps you fit."
He finished the challenge about 36 hours after starting it.