For the first time in human history more than half of us live in cities. Vibrant, complex, colossal - what drives their success? Sao Paulo is a city of extremes. In one day we move across contrasting worlds of wealth and poverty: we risk our lives with the motogirls making deliveries across the city; meet Ayrton Senna's sister as she changes the lives the city's poorest children; and go clubbing with an entrepreneur who controls an entire street of the city's nightlife. Show less