Diana Ross probably isn’t used to being the opening act.

The soul legend captivated a sold-out crowd at the grand reopening of the Kings Theatre in Flatbush on Tuesday night, but the main attraction was the majestic and painstakingly restored venue.

“I couldn’t be more proud,” said Assemblywoman Rodneyse Bichotte (D–Flatbush), as she gazed around the lobby before the show. “It’s so beautiful, so intricate, and it really brings flavor to Flatbush.”

Okay, so the 3,000 people who coughed up upwards of $100 and lined up around the block to see the legendary Detroit diva are probably fans.

Show-goers walking through the lobby of the Flatbush Avenue venue for the first time were agog as they took in the high, ornamental ceilings and dramatic red drapes, all carefully made to appear as they did when the theater opened in 1929.

One new feature of the revamped theater was the more-spacious seats, but no one was sitting down for Ross — she had the whole crowd on its feet within seconds of her grand entrance, striding down the aisle, belting out “I’m Coming Out.” Some fans surged down the aisle after her to dance in front of the stage, and the rest stayed standing and clapping.

Between a dizzying succession of costume changes, Ross delivered a set of hits from her solo career, and more by the Supremes, the legendary Motown trio she led for more than a decade. And, in true diva fashion, she banned professional photography from the show, so that the only record of the night would be blurry Instagram photos, and shots provided by her publicist.

The concert was the first big show at the palatial venue since it closed as a movie theater in 1977. Efforts to restore the Versailles-inspired treasure gained steam under former borough president Marty Markowitz, who went on his first date at the theater back in the early 1950s. But the renovations didn’t begin until 2013, and only wrapped last month.

Markowitz, who now works as an outer-borough tourism czar for the city, was among the host of local politicos who were no less visibly wowed about the theater’s reopening.

Ross is the first act of a 2015 schedule packed with bold-faced names, including Gladys Knight, Crosby, Stills, and Nash, and the Moscow Ballet.

“We’ve got a lot of footprints coming here from all over the city,” Bichotte said. “We are really experiencing an explosion and enhancement of performing arts in Flatbush.”

For those who missed the big show, or those who went and want to relive the magic, the theater is hosting a free walk-through on Saturday afternoon.

Community walk-through at the Kings Theatre (1027 Flatbush Ave. between Duryea Place and Tilden Avenue in Flatbush, www.kings‌theat‌re.com). Feb. 7, noon to 4:00 p.m. Line forms at 11:30 a.m. and closes at 4:00 p.m. First-come, first-served.

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