“It’s like St. Tropez in the 50s!”

“I tell you, it feels like Amalfi in the 70s!”

“It’s got that whole Montauk-in-the-90s vibe!”

If you are lucky enough this summer to find yourself in Comporta, the small Portuguese beach town on the Atlantic Coast, you might overhear some Europeans, as well as a smattering of Americans, buzzing about how they’ve discovered a new paradise.

Sandstone cliffs at Comporta’s Gale beach.

It’s easy to see why. Less than two hours southeast of Lisbon, Comporta is one of a string of villages on the country’s Alentejo coast, the last undeveloped stretch of Atlantic Ocean coastline in Southern Europe—40 miles of unpeopled and unspoiled, altogether unbelievably beautiful white-sand beaches where early-morning surfers share the waves with pods of breaching dolphins.

Yet if foreigners can’t agree on what Comporta is at this moment, the locals can—it’s a place that’s changing. Fast.

Over the past few years, a tsunami of investment money has surged into the area, creating shock waves that threaten to wash away the character and perhaps even the raw, unspoiled natural beauty that now makes this area so desirable to the LondonNew YorkParis set.

All of which means, if you want to see it, see it now. (They say September is the best month to visit.)

Rice fields surround Comporta.

The Alentejo has long been a secret summer sanctuary for some of Portugal’s oldest and wealthiest families, a place where scrub pines, wind-blown dunes, ancient vineyards, rice paddies, and groves of cork trees create a landscape Cézanne surely would have loved. Most of all, it is a place where seaside vistas seem to roll to infinity, thanks to laws that wisely forbid houses from being built within 1.2 miles of the beach.

But the signs of change are all around—sometimes literally. If you enter Comporta via its main road, you’ll see 25 acres of land sealed off by a huge fence and a billboard trumpeting the news that Jacques Grange—the 79-year-old French interior designer and architect whose clients include Sofia Coppola, Aerin Lauder, and Madison Cox, garden designer to Gianni Agnelli’s late wife, Marella—has decided to help turn the tract into something called the Atlantic Club. Scheduled to open in 2024, it will have 21 villas, where prices will start at $3.5 million.

The port in Comporta’s Carrasqueira village.

(The Atlantic Club does not seem to be entirely a business decision for Grange. Not when you consider he may have loaned his name to the project because it gave him the power to preserve the view from the nearby property where he has lived for 30 years.)

If foreigners can’t agree on what Comporta is at this moment, the locals can—it’s a place that’s changing. Fast.

Then there is the Costa Terra Golf and Ocean Club, a 720-acre development from Discovery Land Company. Owned by the notorious developer Mike Meldman, Discovery famously specializes in high-end gated “communities” in the U.S. for the likes of Tom Brady and George Clooney, and the Costa Terra project will feature 300 homes that start at $4.6 million.

A villa at the Atlantic Club.

It’s hard not to think every piece of property is up for sale or being scouted by developers. Each day as I walked the quiet road home from the local beach, I’d pass by ancient stone houses where fishing nets dried on the walls in front, while through the pine trees in back glass-and-concrete modernist homes that looked like they were airlifted in from Bel Air were visible, standing on plots where the homes of other locals were recently sold and torn down.

Farther down the road I could see the vast parcel where JNcQUOI, the group behind Lisbon’s most exclusive private member’s club, as well as a number of restaurants and a forthcoming boutique hotel, are planning to build a residential community that will, according to promotional material, create “an intimate circle of individuals from all over the world.” The material also mentions a “Space Healer & Energy Balance Consultant” as part of the core team. So there’s that.

Prices for Atlantic Club villas will start at $3.5 million.

The clash of visions, between natives who want to maintain what makes the place so breathtaking and outsiders who want to make some money, was sparked in part by Grange and a few other taste-making patient zeroes such as the German painter Anselm Kiefer and the French designer Christian Louboutin, both of whom were introduced to the area by Grange and now have homes there.

The signs of change are all around—sometimes literally.

The French architect Philippe Starck is nearby as well, as is the British abstract painter Jason Martin, and Noemi Marone Cinzano, a countess whose family formerly owned the Italian vermouth company.

The French interior designer Jacques Grange is one of the people behind the Atlantic Club.

Like Grange, Louboutin, whose home is 30 minutes down the road in the town of Melides, has been his own transformational force. As locals will grumble, Louboutin’s presence legitimized the town for other Parisians and sparked a Franco-colonization that left those aforementioned distinguished Portuguese families less than happy. Louboutin’s recently opened five-star hotel in Melides, Vermelho, might have been the nail in the coffin for the dusty town.

“So tacky,” one of those old-line Portuguese said to me, shaking his head, when I asked about the culture clash that has broken into the open in Melides. “It’s all so tacky.”

It’s a word you hear over and over these days in the region, muttered by Portuguese who are alternately frustrated, disgusted, and depressed by deep-pocketed companies looking to cash in and foreigners looking for the next hot place: the locust-like Brits who have devoured Chianti-shire and now are searching for fresh ground; the French who bemoan the Russians who have “ruined” the South of France for them; and the under-40 New Yorkers looking to be cool—and salivating at the idea of getting in early.

The five-star Vermelho hotel.

The surest sign of change came on one of my last nights on holiday. Praia Na Comporta, a new restaurant, had just opened near Pego Beach, and my wife and I and two friends went to check it out. It was the second night it had been open, and there was only one other table that was occupied. While we were looking at the wine list, trying to decide on something—most of the wines listed cost 30 to 40 euros—the manager came to ask if he could be of any assistance. “Can you suggest a nice local wine?” someone asked.

“I have something for you,” he said, and a short time later he returned with a bottle of red, which was met with a thumbs-up by the table. So much so that we were happy to agree to a second bottle.

“So tacky,” one Portuguese man said to me, shaking his head. “It’s all so tacky.”

At the end of the evening, I picked up the tab. So imagine my surprise when I learned that the bottles of wine he suggested to us cost almost 350 euros. Each.

The interiors at the Vermelho.

Now, I’m not a hick. I live in New York. I know how the game is played. And I say from the top: shame on us for not asking up front how much the wine cost. Most of all, shame on us for trusting him.

Still, I called him over.

“Is this correct?” I asked.

“You asked for a good local wine,” he said.

“Right, but—everything else is no more than 40 euros. I mean—”

“You asked me to recommend something. That’s what I gave you.” Then he walked away.

At once, I felt how the locals must feel. In the midst of a breathtaking stretch of beauty, you have to deal with some guy better suited for Nikki Beach.

Then, one of my companions said all that was left to say: “So tacky.”

Michael Hainey is a Writer at Large at AIR MAIL