They steal in from the dead of night, inserting coded cards that open doors and turn on lights. These soundless hours will be interrupted only by the squeak of sneakers, the soft "thwok" of a shuttlecock and the settling of scores.
It's a side of sport you won't see unless you set your alarms to greet the mainly Asian shift workers who gather for their favourite pastime - badminton.
"It's not uncommon at all, especially in summer," says Dennis Greenman, ex-president and current committeeman for Counties Manukau Badminton. "The courts here are available 24 hours and they come in here after their shifts and have a game."
Playing in the sleeping hours has another benefit: you are guaranteed of getting a court, something that has been increasingly difficult to do in recent times. As traditional team sports like rugby and cricket see adult participation rates plummet, badminton is booming.
This delights those who for years struggled at the coalface of the once unloved sport for years. It also creates a unique set of issues.
"In 10 years we literally will not have enough courts to put all these players on," says Waitakere Badminton Association president Peter Beckerleg, surveying a typically packed out club night at their West Auckland hall.
"Ten years? We're already at that point now," says North Harbour's chief executive Glenn Cox.
"We're looking for another facility now but these things don't grow on trees," he says, scanning the high-ceilinged, 11-court facility on the North Shore that, at 10am on a Friday morning, is packed to capacity with adult players.
"Nobody bloody works around here," he jokes.
It was a pattern repeated at all four of Auckland's main centres. Auckland Badminton Association's 12-court Gillies Ave venue was in full use on the night we visited and on an end-of-season Monday night in Papakura, the six-court Counties Manukau facility was also full to overflowing.
"I'm trying to get council to extend our hours but it is quite difficult given our location," says Auckland's John McGregor. "We're trying to meet the demands of the population and for many that means playing late at night. Our courts are packed on weekdays from 3pm until closing.
"We're trying to get data together to work out just how many people play, how they want to play and when they want to play."
With pro shops that offer discount gear and stringing services, small cafes and even smaller (or non-existent) bars, these are largely homespun operations, far from the what you'd see at your average golf club for example - and yet one is booming in popularity and it's not golf.
"What we've seen in recent years is a shift from club play to people wanting to pay-for-play and that has put enormous pressure on the courts," says Paul Shirley, the managing director at Waitakere and father of Dan, a four-time Commonwealth Games badminton medallist.
He's not complaining, merely pointing out the challenges of administering a sport that is outgrowing its resources.
There is no huge secret as to why badminton's population has mushroomed, particularly in Auckland: immigration, specifically Asian immigration.
In the 2013 census more than 300,000 of Auckland's 1.4 million population identified as Asian, up from 150,000 in 2001. By 2038 Auckland's population projects to be more than 2 million and Asians are expected to account for close to a third of that.
"I've been in the sport for more than 30 years," says Greenman, "and there has been a huge change in the demographics. That's seen a strong resurgence in the sport."
With them, they bring diversity, cultural mores and sporting interests. One of those is badminton, which is massive throughout Asia and in particular China, Indonesia, Korea and Malaysia. It is not just eastern Asia. At Auckland's Gillies Ave hall, probably the best known in the city, a Sri Lankan club block books the hall, often very early on Saturday mornings. A number of Bangladeshis play at Waitakere.
When the Herald visits the city's four main venues, a quick head count determined that about 70-80 per cent of the players were Asian.
Badminton has become extremely popular in Auckland schools - "the fifth-most popular," says Shirley, possibly under-selling it - and while several sports have a big adult participation drop-off, rugby and cricket among them, badminton holds its numbers.
Recent research found that that outside of recreational activities like jogging and swimming, more New Zealanders participate in badminton (7 per cent) than any other sport apart from table tennis and football (both also 7 per cent). The numbers would be even more skewed in Auckland.
The North Harbour courts at Forrest Hill are open between 6am and 11pm "365 days a year", says Cox. "It's a public facility, you book online and it's always busy. Week day mornings are always full and the weekends are chokka."
Interclub play takes over after 7pm but the majority of people through the hall don't belong to a club. The associations all say they want to preserve the primacy of the club scene but the economic reality is they could probably make more money if they left the courts open for pay-for-play.
"The courts are heavily booked and we're obligated to support the club structure but that can make it difficult for individuals who have no interest or no ability to join a club to get a game. It's a dilemma," McGregor says.
"We're seeing a big change in the culture in New Zealand," Cox agrees. "You come in on a Sunday and every court is full for every timeslot right up until closing. We're shutting the doors here around midnight.
"It's a change of psyche," Cox says, "that we're still probably getting to grips with as a sport."
Badminton has unique sounds and rhythms.
The game's idiosyncratic dynamics are largely a result of the target object. The shuttlecock is a simple, yet beautiful piece of engineering: a conical collection of 16 feathers embedded into a leatherbound piece of cork. Like a cat always lands on its feet, the shuttlecock will demonstrate its aerodynamic prowess and turn to fly cork first no matter how you propel it.
The small dimensions of the court, the dynamics of the shuttlecock and the power of the world's best players - the fastest shots regularly are clocked at more than 200km/h - creates optical illusions that challenge written explanation: essentially it appears to travel too fast for human reaction.
It is not uncommon for the pros to play 20-second rallies that contain more than 30 shots.
New Zealand does not reside anywhere near the top of badminton's upper classes.
"We're miles off the pace," admits Shirley.
They are a sport caught in that dreaded high-performance purgatory: they don't get any government funding because they can't demonstrate a pathway to medals; they can't demonstrate a pathway to medals because they don't get any funding.
If you look at High Performance Sport NZ's core funding for 2017, you will not see badminton feature.
What the sport needs is a one-out-of-the-box freak to boost its profile beyond the community level.
We're introduced to Roanne Apalisok, a 13-year-old who came to Auckland from the Philippines 10 years ago. She travels more than an hour most days, driven by dad Gammy, from east Auckland to the Waitakere venue.
Already a highly regarded doubles player, many believe she is destined for great things.
Down south at Papakura we talk to 12-year-old Dylan Naera, who has a pogo-stick vertical leap and is committed to move his national ranking from number three to one.
These players are as committed to their craft as any athlete that plays New Zealand's more traditional sports, but it seems crazy to sheet the future high-performance wellbeing of badminton on such young shoulders, no matter how well adjusted they are.
The majority of the players at the halls when we visit have long since abandoned hopes of glory.
It's fair to say the pace of play at ranges between breakneck and sedate depending on the age and quality of the athletes but the enthusiasm appears undimmed by time. You hear a lot of laughing when you wander the halls.
If this all paints a picture of a sporting Utopia where cultural and language barriers are broken down over the net and the congregation ends each night singing Slice of Heaven a capella, then it's misleading.
The colours run a bit muddier than that.
There is a fear that the shift towards pay-for-play is eroding the club culture that was the backbone of badminton's past (and in fact, most sports' pasts). The bar and social takings are negligible and the bulk of those come from non-Asian members.
There is also the fact that few Asian players travel out of their area, so anybody attending the various masters tournaments around the country could be forgiven for thinking they had climbed into a wayback machine and returned to the starched-collar days of the Pursers and Robsons, the first families of New Zealand badminton.
Both Shirley and Cox also acknowledge that some specific ethnicities have assimilated faster than others. Neither would frame it as a criticism but it does create a relatively unique set of circumstances.
"The Koreans especially like to block book the courts and play among themselves," says Shirley.
While he expresses some frustration that this continued isolation makes it difficult to monetise their growing player base beyond court fees, the advantages of the sport's multiculturalism far outweigh any negatives, including, Shirley says only partly tongue-in-cheek, an expanding world view.
"We have a lot of Bangladeshis play here. I know all about the situation in Burma now," he says, referencing the humanitarian crisis involving displaced Rohingya people seeking sanctuary in the Muslim state.
Most of all though, these players and administrators just want it known that there's something pretty special happening in the Auckland, and by extension, New Zealand sports scene. It's just that you have to look in "non-traditional" places to find it.
Samantha McCamish, a national rep who was playing interclub at Gillies Ave when we visited, summed it up best.
"I was in the pub the other night and looked up and saw badminton on TV," she says.
"I feel like people are just starting to realise just how big this sport is."