Eliezer Ben Joel ha-Levi’s Laws of Eruv, a crucial text in the medieval history of the eruv, redefines ancient definitions of space to fit that of a medieval town. It uses talmudic terminology to describe medieval reality; it reinterprets this terminology to fit this reality; and rules in a way that enables the whole Jewish quarter to be seen as one private space. This ruling shows that in medieval Europe the eruv was redefined to encompass the entire Jewish neighborhood. Thus, predating the walled Jewish quarter and Ghettos, the Jews defined their habitats in the town as a close (although not yet an exclusive) Jewish space, and created a city within a city: a Jewish one within the Christian one. This phenomenon corresponds to the rise of the “community” as the boundary line of Jewish identity.