Either that, or he's talking about the adjacent Albert Einstein College of Medicine.
Atop this playground, and much of the rest of the neighborhood, once stood the enormous Morris Park Racecourse, built in what was then Westchester County (and is now the Bronx) to replace the soon-to-be-turned-into-a-reservoir Jerome Park Racetrack as the host of the Belmont Stakes. Morris Park opened in 1889 on a day of "terrific hot weather, which set every one to perspiring in Turkish bath fashion", and was declared by the NY Times to be "the finest race track in the world". But its success was short-lived, and by 1904 it was closed. It was briefly used as an airfield from 1908 to 1910 before being divided into more than 3000 lots and auctioned off, becoming the residential neighborhood it is today.