A 126-kilometre trek from the suburbs through the idyllic Barossa Valley lies ahead for competitors in today's Santos Tour Down Under.
But before they do, thousands of cycling enthusiasts will pave the way ahead of the official competition, taking part in the Bupa Challenge Tour.
More than 4500 cyclists headed off from Modbury at 6.30am.
Other start locations include Kersbrook at 7am, Mount Pleasant at 7.30am and Nurioopta at 11am.
Opposition Leader Tony Abbott is one the estimated 7000 cyclists taking part.
Sky ProCycling prodigy Geraint Thomas takes to today's starting line as Tour leader, King of the Mountains Leader and Sprint Leader.
Tour cyclists depart Modbury at 11am and are expected a little over three hours later in Tanunda.
The first of the Jayco Sprints is at Mount Pleasant at 80.6 kilometres closely followed by the second at Springton at 89.3 kilometres.
Cyclists will arrive at the Skoda King of the Mountain challenge (Humbug Scrub Category 2) at 30.2 kilometres.
DAY 3: Great Britain's Geraint Thomas has won stage two of the Tour Down Under at Rostrevor.
Just prior, he won the steep climb up the famed Corkscrew Hill before making the descent to the finish line just before 2pm (ACDST).
“It was a good day really. I felt good from the start,” said Thomas after the race.
A number of cyclists have been involved in a crash.
DAY 2: A shorter route for today’s cycling action in stage two of the Tour Down Under will be anything but an easier ride, with cyclists to face the much anticipated Corkscrew Road climb.
Starting for the first time in Mount Barker, cyclists will wind their way through 116 kilometres of road into Echunga, the picturesque township of Hahndorf and Cudlee Creek before finishing in Rostrevor around 2pm.
There will be two sprints – the first at 32 kilometres at Echunga and then at Oakbank at 71.9 kilometres.
But all eyes will be on the King of the Mountain Corkscrew Road slog at Montacute.
Riders will already have travelled almost 110 kilometres by the time they reach it with the finish line in site just six kilometres later.
The climb is an Adelaide cycling institution which is well-placed to leave sprinters gagging for air.
According to cycling website cycle2max.com, it has an average gradient of 9.4 per cent over a distance of 2.4 kilometres. Cyclists report having completed it in around eight minutes.
DAY 1: The first stage of competition in the Santos Tour Down Under gets underway today with a gruelling 135-kilometre slog through the Adelaide Hills.
One hundred and thirty-three starters from 19 teams will commence the stage from the suburb of Prospect, on the city’s outskirts, around 11am.
From there, they will head into the northern suburbs and out into the hills through Houghton, Gumeracha, Mount Torrens and Woodside.
Thousands are expected to greet them at the finish in Lobethal, where they are due around 2.30pm.
The quality of this year's racing field is the best in the tour's 15-year history, according to race director Mike Turtur.
"We have about eight national champions, road race champions, from different countries participating so there's quality of the different type of riders, sprinters, all-rounders," he said.
The Tour Down Under is today paying tribute to the centenary celebration of the world’s most famous cycling race, the Tour de France.
“The Tour de France is the most significant event on the cycling calendar and we felt passionate about marking the milestone in some way at the Santos Tour Down Under, particularly as it is also a milestone year for our event,” said Hitaf Rasheed, Events South Australia general manager.
“We are delighted to work with the Amaury Sports Organisation (ASO – owners of the Tour de France) on this project and thank them for their support in bringing five-time Tour de France champion Bernard Hinault to Adelaide.”
A centenary arch has been erected near the start of Stage 1. The arch will also mark the 15th year of the Santos Tour Down Under.