More than half of the world population is living in cities. By 2050 it is expected this will be two-third. Cities are growing explosively. The value of production is increasingly located in cities and so is the majority of wealth. City mayors are influential leaders making direct deals with multinational firms and (inter)national authorities. And we use the facilities created and maintained by city authorities. The cities in which we are living have become more important than the countries we are living in.