Cities are the focal point of religious pluralism, for in cities the cultures and traditions of the world are concentrated. They are, as Lewis Mumford put it, "energy converted into culture." The term "cosmopolis" has long signaled the world-city, and indeed some of the great cities of the world have had a cosmopolitan texture for many centuries. Today, however, the number of new cosmopolitan cities has grown exponentially. While London, New York, and Mumbai may still be the great examples of world-cities, Leeds, Detroit, Boston, and Toronto also concentrate the energies of complex cultures. Even smaller cities, like Fremont, California, have significant Sikh, Muslim, Hindu, and Buddhist populations. What critical challenges have cities faced as they become more religiously and culturally diverse? How have these challenges been faced, negotiated? What new forms of city life are emerging? What new forms of religious life, including rapidly growing interfaith initiatives, are emerging in the urban environment?