What happens in Columbus Park, stays in Columbus Park.

Gamblers have transformed the Chinatown park into an anything-goes, outdoor casino — where high rollers illegally bet big bucks on card games with pots reaching thousands of dollars, and cops turn a blind eye.

The Post visited the park on four separate days over the past week and spotted up to 10 tents raised and drawing hundreds of mostly mid-aged and elderly punters trying their luck on one of the roughly dozen cement and wooden tables.

“There’s nowhere else in New York this is happening,” said a wide-eyed Jason Roman, a 36-year-old photographer stunned by the Las Vegas-style action. “This is casino-level gambling right here.”

Many of the gamblers huddled under the protective wearing masks or chain-smoking cigarettes, as groups of seven played pai-gow poker, Chinese blackjack and other games of chance for money — which is illegal in city parks.

The tables and benches installed in the park’s plaza — named after the Republic of China’s first president, Sun Yat-sen — are supposed to be for eating, relaxing and playing more conventional games like checkers and chess.

But gambling organizers treat them like turf, showing up around sunrise most mornings to ensure outsiders unaffiliated with the games aren’t sitting there, park patrons said. They cover some tables with casino-style green felt.

“They come and sit right next to you, [and] set up the tents right above you [if you’re sitting],” said a Chinatown resident who frequently visits the park. “They make you feel really uncomfortable.”

“They own that!” snapped another resident, sarcastically referring to the tables. “It’s tough for like tourists, and everybody who buy food here.”

The gamblers wearing hoodies, baseball caps and other casual attire waved around hundred-dollar bills each ante. Stone-faced dealers stuffed their pockets with players’ losses – sometimes taking in four figures per hand.

High stakes, low rent

The makeshift gambling den lacks the glitz and glamour of Las Vegas or Atlantic City, but it has the same high stakes and is more convenient.

“People don’t like to go to Atlantic City [to gamble], man!” barked one player from Brooklyn. “It takes two, three hours to get there.”

Last Sunday, granny carts stuffed with plastic bags sat stationary while high-rollers fisted thousands after cashing out big wins. One senior brought a bag of groceries holding leeks and hung them on a nearby bench while playing cards.

The players and dealers mostly speak Cantonese and other Chinese languages, and many rip through cigarette after cigarette per hand, littering the floor with butts and engulfing the tents with plumes of smoke. Smoking, like gambling, is illegal in city parks.

Interaction between players and dealers typically resembles the banter you’d see in any casino: losers whine, dealers snap at people who don’t follow the rules and high-rollers gloat about winning huge pots.

“Everybody lose,” fumed one bettor in Cantonese after a dealer revealed his hand, according to a Post translator. “It’s unlucky that the host has good cards.”

Most of the players and dealers insisted they don’t speak English. Others were tight-lipped about the games

“There’s no organizer — you just stand here and be the host,” insisted one player through the interpreter.

However, reporters saw the same few people deal cards and handle the money bet over the course of four days. And the betting continued, even under the stars. At dusk, the plaza is closed, and dozens of remaining players headed toward the southern end of the park for after-hours gambling, dropping their chips down near a soccer field and a public restroom.

Risky bet

The wild scene is playing out seven days a week in the park located along Baxter, Worth and Mulberry streets — ironically near federal and state courthouses and law-enforcement office buildings.

People caught gambling in city parks face a misdemeanor charge for disorderly conduct, but that pales in comparison to the criminal charges and jail time they would face if busted for running an actual gambling operation like the one that appears to have popped up at Columbus Park.

Persons convicted of promoting gambling, a felony, could face up to four years in prison and $5,000 in fines.

New York’s Constitution prohibits gambling operations, except certain exceptions like state-run lotteries, authorized casinos, betting on horse races, and bingo and other games used to raise funds for religious groups and charitable nonprofits.

And in city parks, it’s even illegal to bet a few bucks among friends. Violators could be charged with a disorderly person misdemeanor.

However, gambling at Columbus Park has existed for decades — just never quite like this, locals said.

Neighborhood merchants and longtime park patrons say authorities have typically looked the other way because the games were low-key and stakes modest.

Wellington Chen, executive director of the Chinatown Partnership Local Development Corp., said many working-class Chinese New Yorkers have historically come to the neighborhood to eat, and then head to gamble and blow off some steam after clocking 70- to 80-hour work-weeks.

“Instead of going to a bar, they go to a park and get some adrenaline pumping,” he said.

But over the past year, interest in the games has grown along with its pots – especially in recent months after organizers began cavalierly raising the tents with little enforcement from city cops or parks peace officers, the merchants and patrons added.

“This is a New York City park; how is this legal?” wondered one patron. “They have tents set up; they’re gambling. What is the city park getting out of this?”

Geoffrey Croft, a city parks watchdog for more than two decades, shouted “Oh, my God!” after being shown photos of the open-air casino.

“Who knew the state gave a gambling license out to Columbus Park,” he quipped.

“I’ve never seen gambling on this scale in a park before, but I guess like the rest of the city these days, enforcement is really lacking.”

Joe Puleo, president of Local 983 of District Council 37, which represents parks officers, said his members don’t strictly enforce the park’s gambling rules because they’re short-staffed and “follow the lead of the NYPD on such issues.”

“It’s amazing that so many people are gambling in front of the courts of all places,” he said. “The only thing worse would be if they were gambling a few blocks away outside City Hall.”

On Friday, two police officers were spotted and photographed standing by the tables watching the gamblers play. They chuckled among themselves and then left a few minutes after without taking any action, according to the shutterbug.

The NYPD said that as of Thursday it had received seven 911 calls this year regarding complaints of gambling at Columbus Park.

Despite the gambling, overall violent crime has been historically minimal in and around Columbus Park with some exceptions.

Last year, a man lost a kidney after a stranger gouged him with an 8-inch blade, at the intersection of Baxter and Worth streets.

Local residents and merchants said they’ve seen cops and parks officers in recent months occasionally demand the tents be lowered — without making arrests or issuing summonses – only to watch game organizers quickly put them back up and start the games again after authorities leave.

Parks Department spokeswoman Meghan Lalor said her agency “is aware” of the gambling “issue” and is working with the NYPD “to enforce the no-gambling rule at Columbus Park.”

An NYPD spokesperson was more cryptic when asked about the gambling, simply saying “the park is used by a large number of individuals from the Asian community on a daily basis for a variety of activities.”