While planners look at how to cut back the energy consumption of big cities, at the other end of the scale are shanty towns-organically evolved and self-built by millions of people in the developing world without a planner in sight. These shanties meet many of the ideas of eco-city designers. They are high-density but low-rise; their lanes and alleys are largely pedestrianized; and many of their inhabitants recycle waste materials from the wider city. From a purely ecological perspective, shanties and their inhabitants are good example of the new, green urban metabolism. Despite their sanitary and security failings, they often have a social vibrancy and sound ecological status that gets lost in most planned urban environments.