National Geographic: Megacities Mexico City

Description: National Geographic: Megacities Mexico City: It's the world's biggest city. It sprawls across more than 1,400 square kilometers. But for the 18 million people who live here, it's not just another metropolis. Mexico City is ground zero. This Mega-city violates the first rule of real estate: location. On one side: one of the world's most earthquake-prone hotspots. On the other: one of the world's most active volcanoes. And beneath their feet - a shaky foundation of landfill. To Mother Nature, Mexico City is one big target. And any moment, the Big One could hit. But against the most destructive force of nature, the city is tapping the power of science. From subways to freeways, Mexico City is harnessing cutting-edge technology to build in safety. Towering over the city is Latin America's tallest skyscraper - built to ride out an earthquake on giant shock absorbers. Most of all, the city is now armed with a slender line of defense: an earthquake detection system, built to give the city a one-minute warning before a quake arrives. Because today, the question isn't if another earthquake will hit - but when