Over 600,000 Jews, particularly Orthodox and Hasidic Jews, have become concentrated in such historically Jewish areas as Borough Park, Williamsburg, and Midwood, where there are many yeshivas, synagogues, and kosher restaurants, as well as a variety of Jewish businesses. Adjacent to Borough Park, the Kensington area housed a significant population of Conservative Jews (under the aegis of such nationally prominent midcentury rabbis as Jacob Bosniak and Abraham Heller) when it was still considered to be a subsection of Flatbush; many of their defunct facilities have been repurposed to serve extensions of the Borough Park Hasidic community. Other notable religious Jewish neighborhoods with a longstanding cultural lineage include Canarsie, Sea Gate, and Crown Heights, home to the Chabad world headquarters. Neighborhoods with largely defunct yet historically notable Jewish populations include central Flatbush, East Flatbush, Brownsville, East New York, Bensonhurst and Sheepshead Bay (particularly its Madison subsection). Many hospitals in Brooklyn were started by Jewish charities, including Maimonides Medical Center in Borough Park and Brookdale Hospital in East Flatbush.