Inside the most unbuttoned night of professional tennis, where Serena Williams and Rafael Nadal faced off for a game of badminton in an iconic NYC hotel's courtyard

Last night, I attended The Palace Invitational, an annual event at a luxury hotel in New York City in honor of the US Open, America's biggest tennis tournament.

Tennis stars Rafael "Rafa" Nadal, Serena and Venus Williams, Cori "Coco" Gauff, Alexander "Sascha" and Mischa Zverev, Sam Querrey, and Daniil Medvedev were invited to the event to face off in a friendly game of badminton.

The event takes place at the Lotte New York Palace, an iconic five-star hotel in Midtown Manhattan.

A night's stay at the Lotte New York Palace starts at about $405.

I arrived to the event about 10 minutes early, as the invitation said to arrive promptly at 5:00 p.m.

I recognized the hotel's iconic courtyard from The CW's teen drama "Gossip Girl," which filmed scenes both in the courtyard and inside the hotel.

In fact, the hotel offers a "Gossip Girl Getaway" package that includes a stay at the hotel and tickets to a tour of the show's filming locations around the city.

After checking in and getting my media pass, I waited on the sidewalk for about 10 minutes before they opened the gates.

A badminton court was set up in the center of the hotel's elegant courtyard.

Barriers surrounded the court to keep the crowd at bay.

There appeared to be at least 50 guests in attendance.

The Palace Invitational is usually open only to media and VIP guests staying at the Lotte New York Palace Hotel.

This year, the hotel offered guests the option to book a $10,000 package that included two nights' accommodation in a corner suite, invitations to the Palace Invitational for four guests, a round of cocktails at the hotel's Gold Room bar, breakfast at the hotel's bistro, and a signed tennis ball from the Palace Invitational Players.

The stylish crowd was a mix of all ages.

Men wore button-down shirts and khakis (and a few wore full suits), while most of the women wore cocktail-type dresses, some with heels but just as many with sneakers or flat sandals.

I didn't feel underdressed in my blue patterned wrap dress and sneakers.

At about 90 degrees Fahrenheit with high humidity, everybody was sweating.

A rosé bar was set up right inside the front gates, and another bar was open near the main doors to the hotel.

The bartenders were serving Chateau d'Esclans rosé, sangria with fresh strawberries and oranges, various sodas, and Icelandic spring water.

I got a glass of the rosé sangria, which came in a plastic cup that looked fancy because of its golden rim.

The sangria was a bit too sweet for my liking, but I didn't even care because at least it was ice-cold. Even though all I was doing was wandering around taking photos, I was sweating profusely.

Servers were walking around with platters of finger foods including tiny sandwiches, Kobe beef sushi, and chorizo rice balls.

The food was all very tiny, which generally seems to indicate that it's fancy.

I was underwhelmed by the Kobe beef sushi, which was "inspired" by Serena Williams — whatever that means — according to publicity materials for the event. I also tasted a chorizo and saffron arancini (rice ball) inspired by Rafael Nadal, which I found to be much tastier.

One intrepid server was offering up snacks on a tennis racket, which seemed to be a bold move.

I could imagine one bump of the elbow would send the tiny pastries and the rosemary leaves flying. Fortunately, I didn't see that happen.

Two young women dressed in white Nike tennis outfits were wandering through the crowd with giant bottles of rosé, refilling guests' cups.

The rosé flowed freely throughout the event.

With the two bars, the two tennis rosé women, and the other servers walking around with cups of sangria, it would be very easy to get tipsy.

A DJ was set up in one corner of the courtyard.

He played mainly upbeat pop songs, including a seemingly neverending medley that somehow combined at least 10 different songs, including Ariana Grande's "God Is A Woman," Lady Gaga's "Shallow," "I Like It" by Cardi B, and "Love Lies" by Khalid and Normani.

After almost an hour, as the guests continued to mingle and drink rosé, there was still no sign of Nadal, the Williams sisters, or the other tennis players.

At about 5:45 p.m., people seemed to turn their focus toward the badminton court, waiting for the tennis players to make their debut.

Finally, at 6:00 p.m., about an hour after the event started, the hotel manager introduced the host of the evening, NBC News anchor Dylan Dreyer.

Dreyer welcomed the players onto the court. The biggest cheer came for Rafael Nadal, followed by the Williams sisters.

Even though I'm not a big tennis fan, I felt star-struck seeing Serena and Venus.

The first match saw Sam Querrey and Alexander Zverev playing against Mischa Zverev and Daniil Medvedev.

The match wasn't particularly competitive, and the players seemed rather amused throughout.

Instead of trying to score points, the tennis stars seemed intent on lobbing the birdie back and forth as high in the air as possible.

The crowd "ooh"-ed and "ah"-ed appropriately.

The match anticlimactically ended in a tie.

Next up were the Williams sisters, Serena and Venus.

They started the badminton match playing against Nadal and Dreyer, the NBC News anchor, but Dreyer quickly said she needed to sub out because she was pregnant.

In a surprise appearance, 15-year-old tennis star Cori "Coco" Gauff showed up to take Dreyer's place to play alongside Nadal and face off against the Williams sisters.

Gauff was the youngest player to ever qualify for the main draw at Wimbledon.

But, as it turns out, tennis and badminton skills aren't exactly the same: Her racket missed the birdie the first several times she swung at it, and when she finally managed to hit it, it didn't go over the net.

Nadal, for his part, didn't seem to mind in the slightest, laughing good-naturedly even though they were losing.

Pop music blasted throughout the courtyard amid occasional cheers from the crowd. Laughing and joking their way through the badminton match, none of the players seemed too concerned about winning.

Serena and Venus ended up taking the trophy for the second match.

Both of the badminton matches were over in about 20 minutes.

Afterward, the players spent a few minutes posing for photos together.

A couple of the players tossed tennis balls to lucky onlookers in the crowd.

After that, the players disappeared into a side door into the hotel.

I was slightly disappointed that they didn't stick around to mingle for a few minutes.

People started filtering out almost immediately after the badminton matches ended, but some lingered to finish their conversations and their drinks.

At about 6:50 p.m., the DJ turned the music volume way up. Whether that was to turn the event into more of a party or to get people to leave, I didn't know. As the courtyard was emptying out, I took that as my cue to head home.

Apart from the roughly eight-minute match between Nadal, Gauff, and the Williams sisters, there wasn't much excitement during the two-hour event — but the evening was clearly meant to be a low-key affair.

Considering the crowd of wealthy and stylish VIP hotel guests, it's a safe bet to assume many of them will attend the US Open itself, where the true drama and excitement will be found.