"A breeding ground for violence" the mayor of Molenbeek called her borough on Sunday, speaking of unemployment and overcrowding among Arab immigrant families, of youthful despair finding refuge in radical Islam.
But as the Brussels district on the wrong side of the city's postindustrial canal becomes a focus for police pursuing those behind Friday's mass attacks in Paris, Belgian authorities are asking what makes the narrow, terraced streets of Molenbeek different from a thousand similar neighborhoods across Europe.
Three themes emerge as Molenbeek is again in a spotlight of Islamist violence, home not just to militants among Belgium's own half a million Muslims but, it seems, for French radicals seeking a convenient, discreet base to lie low, plan and arm before striking their homeland across the border: