The outside of 25 Joralemon St. in Brooklyn Heights. Eagle photo by Noah Goldberg.

A badly decomposed body was found in the basement of a swanky Brooklyn Heights building Wednesday, police said.

Cops responded around 9:50 a.m. to a call reporting an unconscious man in the basement of 25 Joralemon St., a low-slung residential building bordering the Brooklyn-Queens Expressway. Emergency Medical Services responded and pronounced the unidentified man dead at the scene. It was not immediately clear how long he had been dead.

There is water in the basement of the building, police said, but it was unclear if the body was found floating.

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25 Joralemon St., built in the early 1900s, used to be a city-owned water pumping station, but has since been converted into a luxury co-op called Pumphouse Mews, with apartments on the market for $3 million.

The Office of the Medical Examiner will determine the man’s cause of death.

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