Walk along Lenox Avenue in the heart of Harlem on a Sunday morning, pass the Mt. Olivet Church and you’ll hear the gospel choir singing passionately, worshippers and gospel-lovers streaming into the church in their Sunday best.

But look up, toward the top of the towering Grecian columns, and you’ll find Stars of David.

Built in 1907, this church was once the prestigious Temple Israel, led by Rabbi Dr. Maurice Harris. The congregation was initially Orthodox but over the decades became Reform under the rabbi’s leadership. The doors of the Torah ark are still there, but behind them now is a baptismal pool. A balcony, once the women’s section, now offers a second tier of seating. In 1920 the congregation moved, together with most of its families, to a new building on the Upper West Side.

Image by Avital Chizhik-Goldschmid... A Star of David decorates a column of Harlem's Mt. Olivet Church, formerly the Temple Israel synagogue.

Harlem is full of Jewish symbols, fragments of an older time, if you only know where to look. The cornerstone of the Mount Neboh Baptist Church, on the corner of 114th Street and Adam Clayton Powell Jr. Boulevard, is inscribed with the Jewish year 5668. The enormous Baptist Temple Church, on West 116th, has Stars of David at its top corners — remnants of Congregation Ohab Zedek, an affluent synagogue whose cantor was the renowned Yossele Rosenblatt.

The Salvation and Deliverance Church was once the Institutional Synagogue. The first Orthodox synagogue to also offer recreational services, known as the “shul with the pool,” it was the very first synagogue to try to bring Jews closer to Judaism through other portals, using the “come to play, stay to pray” mantra.

Image by Google Earth The Old Broadway Synagogue is the last operating shul in Harlem.

“Harlem was one of the first communities which actively addressed the question of how to keep children of Jewish immigrants Jewish, in an environment where they’re rapidly Americanized,” notes Jeffrey Gurock, professor of Jewish History at Yeshiva University and author of “The Jews of Harlem: The Rise, Decline and Revival of an Urban Jewish Community,” to be published in the fall.

Gurock has devoted decades to studying Harlem’s oft-overlooked Jewish history. “I always receive a very welcome attitude from Harlem’s church leaders, when I tell them about my research findings,” he says. “They say that the iconography reminds them of their Old Testament roots.”

In 1900, after Krakow and the Lower East Side, Harlem was the world’s largest Jewish community, with 180,000 Jews making northern Manhattan their home, according to Gurock.

The community consisted mostly of second-generation German Jews, children of immigrants who had made it in America, mostly families who had grown up on the Lower East Side yet chose to flee the influx of religious Eastern European Jews at the turn of the century. “‘Yiddishkeit culture’ was not for them,” says Martin Shore, a historian with the Lower East Side Jewish Conservancy, who leads Jewish-themed tours of Harlem. “So they headed uptown, to the brownstones of Manhattan’s high 100’s, to Harlem.”

There, a small Jerusalem began to flourish: the Harlem Workmen’s Circle, a Talmud Torah, yeshivas, kosher butchers, Blumstein’s high-end department store. An opera house (managed by Oscar Hammerstein I, a German Jew and member of Temple Israel), popular among Berlin’s and Vienna’s Jewish exports, featured Shakespeare and operas along with more popular shows. Eventually, 125th Street would become a small theater district — most famously featuring the Apollo Theater, developed into a venue for the black community by one Sidney Cohen.

And just as in other Jewish enclaves, social issues brewed in Harlem. When rent strikes and butcher strikes hit the Lower East Side, within 10 days, Harlem’s Jews were out in the streets too. Once, Jewish housewives chained themselves to the elevated-train tracks, refusing to budge until the price of kosher chicken went down.

As the African-American community began to move into the neighborhood, external tensions appeared as well. “If you want to understand Jewish-black relations, you have to look at it at the neighborhood level,” Gurock says.

Relations were mixed: At Blumstein’s Department Store, blacks were not hired, and black women could not try on dresses in the fitting room, until civil rights activist Adam C. Powell launched a neighborhood-wide campaign for businesses to hire black workers across employment levels. In response, Blumstein’s retracted their racist policy and began hiring African Americans, using black models and mannequins, selling cosmetics for nonwhite skin tones — and featuring New York’s first black Santa Claus.

The neighborhood seemed to give its nod of approval: In 1945, Harlem’s largest newspaper, The Amsterdam News, profiled Arnold Blumstein as one of Harlem’s top 10 businessmen. Jewish entrepreneurs knew how to cater to their locale: When music clubs, which often featured great African American performers, wouldn’t let in black patrons, Jewish mobster and integrationist Arnold Rothstein (who appears as Meyer Wolfsheim in F. Scott Fitzgerald’s “The Great Gatsby”) fought for clubs to be open to all.

Perhaps most interestingly, several communities of self-identified black Jews emerged here, too. The most prominent group gathered at The Commandment Keepers’ Holy Church of the Living God, a congregation based in a mansion, led by Rabbi Wentworth Matthews — a Nigerian immigrant who had moved to Harlem in 1919 and taught himself Judaism, eventually appointing himself as a rabbi. The community followed Sephardic liturgy, observed holidays, practiced circumcision, and had its own kosher butcher.

“They called themselves Falashas,” a term used to refer to Ethiopian Jews, says Marty Shore. “Though they were not Ethiopian themselves, they associated themselves with the Jews who were found in Ethiopia’s small villages where primitive Orthodox traditions were kept,” he says.

The lifespan of the robust Jewish community in Harlem was short — by World War II, most had left. “With the growth of communities in the Upper West Side, Brooklyn and Washington Heights, Jews were pulled out of Harlem as opposed to pushed out,” says Gurock, whose own father grew up in a Harlem tenement. “The idea that Jews are afraid of African Americans moving into their communities wasn’t a reality then.”

Today, a single synagogue of Harlem’s past remains: the Old Broadway Synagogue, a small but resolute congregation with 45 member families.

“I am honored to be able to help a historic community grow and flourish and become a place of Torah and prayer in Harlem,” says Paul Radensky, long-time president of the synagogue and manager of education programs at New York’s Museum of Jewish Heritage.

“The neighborhood is in some ways changing. There is increasing gentrification and Columbia University is building a new campus a couple of blocks away. We hope that the congregation will continue to grow, in its learning, its services offered, and in the number of congregants. We expect that the Jewish population will continue to grow, and we plan to be there for them.”

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