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Forget rooftop pools and heated dog runs — Brooklyn’s hottest new luxury building feature is a famous neighbor!

Developer Two Trees is paying a celebrity resident of its ritzy new Fort Greene high-rise to tweet about how great living there is — and is marketing her presence in the building as “an amenity” for other residents.

Fashion blogger and actress Tavi Gevinson is raking in an undisclosed sum to write glowing posts about the builder’s new tower at Flatbush and Lafayette avenues — now called “300 Ashland,” but formerly and better known as BAM South.

“Tonight I spent a long time admiring/trying to understand this 3D CLOUD-SLASH-MIRROR in my new lobby #adamfrankinc #300AshlandPartner,” wrote Gevinson — the former wunderkind behind teen web-zine Rookie and now Broadway star — on March 13, joining photos documenting her move-in to the building, and her delight at living next door to the Brooklyn Academy of Music.

The ad-tweets were first reported by New York Magazine.

Now, the developer plans on moving in additional famous residents — and the stars will be hosting “special experiences” in the property for their less-well-known neighbors.

“We think it’s an exciting addition to our marketing efforts and a terrific amenity for tenants,” the company said in a statement. “Stay tuned for more great names and content.”

Gevinson pays rent to Two Trees, company spokesman Joshua Berkman claims — and units in the building currently run from $2,416 a month for a studio to $5,479 for a two-bedroom — but the firm also pays her for the sponsored posts, and it isn’t clear on which dollar figure is higher.

He also refused to say how she ended up living and tweeting in the building — if she was invited to move in, or if the company is just taking advantage of a famous tenant.

People who are paid to shill on social media are supposed to make it “clear and conspicuous” when their posts are ads, according to the Federal Trade Commission — which advises starting a missive with “sponsored,” “promotion,” or “ad” — and consumer advocacy group Truth in Advertising told the blog Jezebel that “#300AshlandPartner” may not be sufficient warning.

Two Trees believes they’re clearly ads, according to Berkman, although he says Gevinson is the one penning the posts.

Celebrities are hardly the building’s only selling point — the tower will also house a new Brooklyn Academy of Music cinema, an Apple store, a Whole Foods, a public library branch, and a new home for Museum of Contemporary African Diasporan Arts.

But competition is fierce in the neighborhood, and Two Trees is vying to win moneyed tenants against several other new luxury high-rises nearby, including “the Ashland” next door, which has its own fancy food court, and “The Hub” across the road, which will have a huge indoor pool.

Gevinson could not be reached — by phone, e-mail or tweet — for comment.

Reach deputy editor Ruth Brown at rbrow n@cng local.com or by calling (718) 260–8309. Follow her at twitt er.com/ rbbro wn.