For the first time in human history more than half of us live in cities. Vibrant, complex, colossal - what drives their success? Mexico City is the city that never gives up. In one day in the earthquake capital of the world, we discover how the city's architects keep skyscrapers upright; go wrestling with the masked fighters of Lucho Libra; and venture out in a police patrol car as they fight to defeat the city's criminals. Show less