It’s just past noon on Sunday at the Riviera, and the 60-year-old hotel is starting to welcome its final guests.

The property will close for good in 24 hours, but for a split second, it still feels like any other day of business.

“Just for the one night?” a registration desk clerk asks at check-in. (The Sun paid for a room Sunday evening).

Reality quickly sets in as the clerk recognizes his mistake.

“It’s hard to break that habit,” he says.

Although the hotel operations are still humming along in a largely normal fashion early that afternoon, plenty of signs — literal ones — remind guests that the end is near.

One such sign by the check-in area states plainly that the Riviera closes at noon Monday, and everyone needs to be out by that time.

“Thank you for 60 wonderful years,” the sign reads.

The Riviera has been on a fast track for the history books ever since the Las Vegas Convention and Visitors Authority bought it for $182.5 million with plans to replace it with convention space. So Sunday and Monday was a poignant opportunity for longtime employees, regular guests and local residents to experience everything about the hotel one last time.

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A couple of people at the hotel beauty salon are packing up boxes while snacking on pizza mid-Sunday afternoon.

For co-owner Mina Mahboubi, this isn’t the first time she’s said goodbye to a historic Las Vegas hotel. Mahboubi worked for 28 years at the Stardust, which stood across the street from the Riviera until it was imploded in 2007.

Mahboubi was caught off guard by the fast timing of the Riviera’s closure, given that the hotel had survived bankruptcy and ownership changes before.

“It was a shock for us,” she said.

But she, like everyone else who works at the hotel, is moving on, although her only immediate plan after wrapping up her business was to get much-needed rest.

A few hours later at the “top of the Riv” penthouse, dozens of people are gathering for the finale of a pool tournament. It’s hosted by the American Poolplayers Association, which has come to the Riviera for 23 years.

Marketing Director Jason Bowman says that although his group already made the nearby Westgate the site of future tournaments, it will miss the Riviera dearly — especially the employees.

“These are people that you’ll never see again that you have gotten used to seeing twice a year, for about a month of the year,” Bowman said. “You know them by first name; you know about their lives. They’re almost like co-workers of ours, although we work for different entities.”

The Riviera is important to Bowman on a personal level, too — it’s where he met his wife. They were both working for the poolplayers association but hadn’t interacted much until one fateful trip to Las Vegas.

As dusk falls over the Las Vegas Strip outside, the Riviera’s exterior lights turn on to beckon tourists for one final go-around.

Out front, visitors are regularly stopping for photo ops with the iconic “Crazy Girls” statue. Its ladies with their bare behinds have long been a fixture at the Riviera’s entrance on Las Vegas Boulevard.

Annette Simons, a 24-year-old Las Vegas native, needs to spend time with the statue — and the Riviera in general — while she still has the chance. She often visited Circus Circus across the street as a kid, but she never became familiar with the Riviera.

She knows it’s important to Las Vegas history, though, so she came with a friend to explore during its last night.

“I wish I could go back in time and see it when it was in its prime,” she says.

Later in the evening, local resident Michael Hewitt, 37, is also wandering around the Riviera for a final peek. Unlike Simons, however, Hewitt is intimately familiar with the property: He began going there when he was about 5 years old because it was where is aunt stayed when she was in town.

Local history is important to Hewitt. So important, in fact, that he has an armful of tattoos paying tribute to hotels of Las Vegas past. The Stardust, the Frontier and the Dunes are among the names emblazoned in ink on his arm.

The Riviera would be a natural addition.

“Any of these buildings, in any other city, that are this old and this legendary would be historical landmarks and wouldn’t be touched,” he says. “But here, we just knock them down and rebuild over everything.”

Hewitt has another reason to be sentimental about the Riviera closing: It’s his birthday.

Like Hewitt, Larry Edwards is caught up in nostalgia — he’s on his way to pay his respects to the venue where he performed in “An Evening at La Cage” for about 15 years.

Edwards remembers how enamored he was with the neon lights at first and the many prominent entertainers, such as Frank Sinatra and Liza Minnelli, who performed at the hotel.

“I was just in awe of the glitz and glamour of Las Vegas,” Edwards said.

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By the time the Riviera’s final morning gets under way, any semblances of normalcy are disappearing fast.

Suitcases and cameras are ubiquitous. People are taking an unusual number of selfies with slot machines and table games. Workers are erecting a chain-link fence around the pool.

Every so often, these signifiers of the hotel’s demise are juxtaposed sharply by loud interruptions to the background music.

“Be sure to join the Riviera Rewards club today,” one blares. “Membership is always free!”

Glenn Comeau, a longtime shoeshine at the Riviera, describes having an “eerie feeling” about the closure. Sitting at his chair near a restaurant on the casino floor, he says he may have already had his last customer.

“I wasn’t expecting it to come this quick,” he says. “But, you know the old saying: ‘It is what it is.’”

Outside, the “Crazy Girls” statue has been removed from its longtime home, and a crew is loading it onto a truck. Onlookers crowd the area to document the transition. They cheer as it’s finally settled into the truck bed.

Derek Stevens, CEO of the D hotel-casino in downtown Las Vegas, is watching the action. He’s also a Riviera board member, and he feels sentimental about the closing, now roughly one hour away.

“This is a Vegas icon,” Stevens says. “A lot of memories in this place.”

Stevens is helping part of the Riviera live on by acquiring its slot machines, which he says will eventually make their way to the D and the Golden Gate. He’s also bringing on at least one Riviera employee: Comeau, who should soon start a new job as a shoeshine at the D.

The “Crazy Girls,” statue, meanwhile, is bound for Planet Hollywood, according to Stevens.

Back inside the casino, the tables are bereft of dealers. Paul Carbone, a 52-year-old stockbroker from Vermont, is sitting quietly at one of them, taking in the final moments. Carbone learned about the closure in February after returning from a trip to Las Vegas. He immediately booked a stay for the final days.

“When I look at Las Vegas, I see all the themed casinos, but there’s something really wonderful about the Riviera,” he says, evoking the property’s classic feel. “Now that the Riviera is going, there really isn’t a casino in town that throws us back to those days.”

When the clock finally strikes noon, the now-bustling casino floor erupts in applause. But almost no one is in a hurry to leave. The casino bar is still crowded, and people continue to gamble.

A few minutes later, the activity is interrupted by an announcement.

“May I have your attention, please: The Riviera is officially closed,” a disembodied voice declares. Then, a few minutes later, another announcement reiterates: “Please vacate the premises immediately. Thank you.”

Eventually, security officers move through the casino, making sure that stragglers follow those directions.

On their way out of the rapidly emptying casino, Wisconsin residents Robert and Laura Jansen pause for one more moment.

Laura Jansen says they kept gambling after the end was announced — until they were told they had to stop. They’ve been coming to the Riviera for years, so they didn’t want to depart until it was absolutely necessary.

But it’s past 12:15 p.m. at this point; security is getting more insistent now.

“Come on,” Laura Jansen says, gently pulling her husband’s arm. “We’re getting kicked out again.”

And then they walked away, leaving the Riviera, and its six decades of history, behind them.