(CNN) Had it not been for a neighbor, the greatest mountain-bike rider of all time might still now remain undiscovered.

But 21 years on from a Sunday morning ride with a cycling enthusiast living next door, now is the beginning of the end to the remarkable career of Julien Absalon

The only rider in history to win five world cross-country crowns, he also boasts two Olympic titles and could have had a third at London 2012 had it not been for a puncture.

Olympic gold number three remains the target: Rio de Janeiro in seven months' time is earmarked as the swansong of the sport's greatest exponent.

"It will be the last challenge of my career," he tells CNN's Human to Hero series . "I will stop after that, so the goal is to have a third gold medal."

That failure at London 2012 still haunts Absalon, and still drives him to add to his numerous successes.

Then at the peak of his powers, he was the clear favorite to triumph again. But he punctured on the opening lap of the race, and by the time he'd repaired it he was 55 seconds behind his rivals, so pulled out knowing a medal of any color had gone.

Good coach this morning! @remyabsalon #ride_bmc A video posted by Julien Absalon (@julien_absalon) on Dec 30, 2015 at 9:45am PST

"London 2012 was for me the worst moment of my career because I was really focused on it after Athens and after Beijing -- two victories in a row," Absalon says. "But I had no chance to defend my title because I had a flat tire immediately after the start."

His first Olympic title in 2004 was something of a surprise, with Absalon then seen as an outside bet for victory.

"When you stand up on the Olympic podium, it's incredible. You cannot explain the emotion you have when you work so hard during a lot of the season," he says.

"It's not possible to realize immediately. You are like in a dream and you say, 'Is it true or not true.' Maybe it takes two or three weeks to understand."

It is all a far cry from the 14-year-old Absalon, who was approached by a neighbor to ride alongside him for the first time.

A few more rides later, the Frenchman found he was such a natural that his neighbor suggested he should enter competitions, and Absalon returned to the family home to say to his parents, "Yes, that's what I want to do."

Four months into riding in the professional ranks, he finished fourth at his national championships, and within two years he was world champion for the first time.

It was the beginning of a love affair that shows no signs of diminishing more than two decades on, even if his competitive life is drawing to a close.

"What I like so much is to be in the nature," he says in his slightly broken English. "I need to be outside. For me, it's a necessity to be outside and to do sport outside in the nature.

"Because when I am outside on my bike I just feel good because I do what I like. I feel free."

JUST WATCHED Downhill mountain biker reaches peaks Replay More Videos ... MUST WATCH Downhill mountain biker reaches peaks 02:52

JUST WATCHED Bike ride with a breathtaking view Replay More Videos ... MUST WATCH Bike ride with a breathtaking view 01:32

Growing up in Remiremont, northeast France, Absalon was a keen exponent of judo and skiing, sporting passions he says helped him learn to fall -- a talent he has had to master with all too much regularity on his bike.

Such spills at speed have led to a litany of injuries. "I broke my collarbone, I broke the radius (in the forearm) twice left and right, I broke eight ribs in four crashes. Maybe it's easier to list the things I haven't broken," says Absalon, who fell and hurt his side at his BMC team 's training camp in Spain the day before meeting CNN.

But while mountain biking has left a physical mark on him, his mark on the sport is indelibly bigger -- Absalon was a dominant force who often gave the impression to rivals he had the race won even before leaving the start.

In 2014 he won his fifth world title -- seven years after the previous one -- and was runner-up in 2015, beaten by Swiss rival Nino Schurter on the last lap.

His farewell comes on the final weekend of Rio just days after his 36th birthday, and the preparation will be like any of the multitude of races to have gone before.

"So it's the same each time -- one hour before the race I leave the bus and I like to find a quiet place to warm up, to focus on the race and also prepare the body for the start.

"Because in mountain biking, the start is really important. We need to start really fast, so you need to prepare for that.

"(In the race) you need to go as fast as possible to take some risks but don't crash, that's the challenge."

Despite the aforementioned list of painful falls, Absalon rides without fear for one simple reason: "You don't have fear because if you have fear you crash or you go really slow.

JUST WATCHED Rider tries double backflip on mountain Replay More Videos ... MUST WATCH Rider tries double backflip on mountain 00:34

"We know what we need to do... and I think it's not really dangerous because we often crash but don't have lots of big injuries."

A compact rider -- measuring in at 1.80 meters (5 feet 9 inches) and 68 kilograms -- he trains between two and five hours a day, and makes no secret of the fact that he is infinitely more at ease on two pedals than on two feet.

"When I am riding I have more ability than on my feet," he admits. "When I am on the bike, it is automatic mode. So it's part of me."

The tag of being the best of all time does not sit particularly comfortably with Absalon, who does not readily relish the spotlight, but the time is approaching when he will dwell on his remarkable list of achievements.

"When people say I'm the best mountain biker in the world I am happy, but I don't realize it very much because I am a competitor so I have some goals," he adds. "When I will stop, I will look back and say, 'OK, I won this, this, this ...' but for the moment I prefer to look at the future."

The clock is ticking to Rio and one final ride.