Sixteen kilometres down the road from Tharwa, one hill has been tackled by cyclists repeatedly for decades, not as part of a race, but just for the sheer challenge.
On Sunday, almost 30 years to the day after the first event, more than 1000 cyclists will line up to tackle Fitz's Hill.
Hamish Jones will be among the cyclists on Sunday and he headed out for a final ride before the event on the road up to the Mt Stromlo Observatory on Saturday.
Mr Jones said he usually rode the course by himself for the personal challenge, taking it fairly easy on the day.
"I'm a very casual rider, really," he said.
Mr Jones first took part 15 years ago in the 50-kilometre course, building to the classic 155-kilometre course, which he has now completed four times.
He said his training regime started off with weekend rides around Canberra, increasing the distance each time.
"I usually like to tackle the hills around the lake, Mt Ainslie, Black Mountain and Red Hill."
There was a good atmosphere on the day with a range of riders, he said.
"Amongst the people who are really just there to give it a go and make the achievement themselves, maybe for the first time, there's a good attitude of friendliness and you can have a ride next to people for a while and have a chat."
The event has come a long way since 37 cyclists lined up on Eucumbene Drive in Duffy for 100- and 150-kilometre courses in October 1989. Organised by John Pitt and bike shop owner John Harvey with the Canberra Cycling Club, the first Fitz's Challenge was at the forefront of similar cycling events around Australia.
Greg Cunningham, who first rode the challenge in the early 1990s before going on to become one of its organisers, said it had become an institution in the Canberra cycling community - and had strong national following too.
Mr Cunningham said that on a recent ride near Shellharbour in NSW, he pulled alongside some other riders from Sydney who were excited to be heading to the capital to tackle Fitz's.
The roads south-west of Canberra were perfect for a cycling event like the challenge, he said. There was little traffic and plenty of hills for riders to tackle.
He said it was little wonder the event had survived and thrived for 30 years, offering an inclusive event for a range of cyclists in a period where the activity had become more popular.
"It enables people to progress. One year, [they] do the ride out to Tharwa and back and the next year [they] try one of the longer distances, and improve their riding that way. And train for it, to see if they can extend their distance," he said.
Although Mr Cunningham had moved away from Canberra, he said his memories of the challenge were fond ones and he hoped to come back and ride the course again.
"It's a very special memory to remember Fitz's and all the rides I used to do out in that area," he said.
Pedal Power ACT has run the event since 1998, taking over from the Veterans' Cycling Club.
Slower speed limits will be in place on roads that form the courses for the event, including Uriarra Road, Brindabella Road, Paddy's River Road, Tidbinbilla Road, Naas Road and Boboyan Road. Riders tackling the longest courses will set off at 6am on Sunday, with cyclists expected to be on the roads until after 7pm.