The World Bank estimates that the number of urban poor will almost treble to 1500 million by the year 2025.1 At least 600 million people, most of them poor, already live in health-and life-threatening situations in decaying urban environments. A third of all city dwellers live in substandard housing. At least 250 million urban residents have no ready access to safe piped water, and 400 million do not have adequate sanitation.