As the world’s population grows increasingly urban, we look back at history's greatest cities, from the modern metropolis to the ancient polis. Among the contributors: Jane Jacobs, Italo Calvino, George Packer, Theodore Dreiser, Vitruvius, Jules Verne, John Hersey, E.B. White, Luc Sante, Samuel Pepys, Jorge Luis Borges, Christopher Wren, Marguerite Duras.