It's the day where Auckland comes out to run. The Round the Bays run is New Zealand's largest mass participation sporting event.
It attracts 42,000 registered runners, and a total of more than 70,000 take part in the run that dates back to 1972.
"It is a true celebration of Auckland," said organiser Elizabeth Leitch from Pants Events.
"It's one of Auckland's iconic events, and almost a rite of passage to take part in Round the Bays at least once. We are expecting more than 70,000 to take part on the day and hope to encourage more to officially register - around 30,000 don't officially register or pay. We're really encouraging people to register, as the proceeds go to children's charities."
Each year four to six charities receive donations from the race of about $120,000.
The 8.4km run, sponsored by Ports of Auckland, winds around the bays from Auckland City to Vellenoweth Green in St Heliers and is a real leveller.
It attracts business teams, with everyone from the factory floor to the CEO's office taking part in the race.
More than 80 per cent of participants do the run as part of a team.
Athletes of all abilities and ages take part, and is it a great day for the community. Last year, participants ranged from babies pushed in prams to 200 people aged over 75.
"With an easy, flat course along the stunning Auckland waterfront, it's an achievable distance for most people," said Leitch.
That ethos of including everyone will please its founders who created the event more than 40 years ago. The Round the Bays was initiated by the Auckland Joggers Club in 1972.
The first run attracted 1200 participants and started at the Auckland Town Hall, going down Queen St and along to St Heliers.
Running historian Garth Gilmour said it was one of the first "fun-runs" in the world and became the inspiration for other runs around the world.
The original 1200 field swelled in three years to 5000, in four to 12,000 and kept growing until about 80,000, nearly half of whom were unofficial runners, took part in 1982.
Leitch has a couple of standout memories of the event.
"One year Hamish Carter turned up, ran and won easily. It was as if he'd been out for a long training run and tacked Round the Bays on the end - he was so relaxed.
"The other, who epitomises a lot of what I love about this event, was the late Raymond Glasgow. He was 95 when he took part in 2008, and had participated enthusiastically for many years. Seeing him alongside his son and grandson is a special memory," Leitch says.
Organising the event is a huge task for the team in charge.
"The biggest challenge is there are no dress rehearsals, we have one chance to get it right on the day," says Leitch.
The sheer scale of the event is shown by the 18km of traffic signs, 222 portable toilets and 100,000 cups required.
Ports of Auckland chief executive officer, Tony Gibson says Round the Bays is a day for Aucklanders to celebrate their harbour and waterfront.
"Auckland's port has been an iconic part of the city's waterfront for over 100 years, and we're proud to again be the principal sponsor of this fantastic Auckland event.
"Round the Bays is the perfect way for businesses to enjoy themselves while supporting outstanding projects. From the smallest office to the biggest corporate - each can select a great charity or project that they feel a particular affinity with and have fun while doing it."
What advice do organisers have for people running the Round the Bays for the first time?
Leitch: "Drink plenty of water, take it easy and most of all have fun. If you haven't done much training, don't overdo it - just go at your own pace and enjoy the people-watching.
"There is plenty to see and do along the route. Most of all, have fun. There is a lot to see along the way, including giant sprinklers, hot dog stands, and some great costumes."
Round the Bays
Date: Sunday, March 10
Start: Quay St, next to Vector Arena between Tinley St and the Strand overbridge (no public access via the overbridge)
Finish: Vellenoweth Green, St Heliers Bay
Cost: Adults $15 Children (age 6-16) $10. Free entry for children 5 and under.
Late registrations: Available until 9am on the day.