Siren song.

Emmy-nominated production designer John Paino exclusively told The Post that the lavish mansion in the Netflix series “Sirens” was real, not just a set. 

While the interior scenes were shot at a soundstage in Williamsburg, he noted that the exterior scenes of the house were filmed “on the north shore of Long Island near Southold.”

Paino, who also did production design for “Big Little Lies,” “The Morning Show,” and “The Last of Us,” said, “It is a summer home of very wealthy people, so we actually did a little scouting in Boston to look at some outrageous houses of some of the rich.”

He added that the particular mansion they picked “has a certain white New England look to it,” teasing, “This house is on steroids – everything is big boned and dialed up to 11.” 

Now streaming on Netflix, “Sirens” follows Devon (Meghann Fahy, “The White Lotus”), who thinks her sister, Simone (Milly Alcock, “House of the Dragon”), needs to be rescued from her new job. Simone has been working for the wealthy socialite Michaela Kell (Julianne Moore), who Devon thinks is running a cult at her lavish beach estate. 

Kevin Bacon co-stars as Michaela’s husband, Peter, and “It’s Always Sunny in Philadelphia” star Glenn Howerton plays their friend and Simone’s boyfriend, Ethan. 

To get the right look for Michaela’s home, although they used the real façade of the Long Island house, they added to it, Paino said.  

“Basically, the house was not big enough. We built façades on top of it to make it appear bigger. The style is based on old architecture with nods to classical Greek architecture, like the temple of Delphi,” he added. “That’s why we have our atrium interior, which feels like a big museum.”

There’s a scene in “Sirens” when Ethan accidentally takes a drunk plunge off a cliff. Paino said the house really was situated “on a beautiful cliff – which was important to our story. It had great views of the ocean. The house was a starting off point. We added pergolas and façades and part of a turret.”

He added, “A bit of it was influenced by Nantucket.” 

Paino said that his inspiration for the color palette, which includes preppy pinks and pastels, was the 1965 film “Juliet of the Spirits” by Federico Fellini. 

Since he worked on “Big Little Lies,” the production designer is no stranger to creating the aesthetic of the uber-wealthy. 

The key? “I think an outrageous dressing room and wardrobe area. We had some really nice ones here… the wardrobes and closets showcase things for that kind of wealth. So [‘Sirens’] was ‘Big Little Lies’ really ramped up,” Paino said.

His favorite set piece on “Sirens” was the 40-foot anchor on the front lawn. 

“That was fun and that tells you a lot about Michaela. When you go around to places in New England, you see anchors on people’s lawns,” Paino said.

He added, “That was my idea because I had just seen so many anchors. In theory, the husband’s wealth is ancient from old New England whaling. It’s conceivable that there would be an anchor that big. And, we made sure the barbs on the end look like birds’ claws as a nod to Michaela.”