Cities, like bodies, grow and evolve. In the case of New York City, that growth never would have occurred if not for a Homeric engineering feat that occurred mostly underground. Jad digs into the history of the city's water tunnels with Diane Galusha and Nik Sokol. And Sandhogs Ritchie Fitzsimmons and John "Chick" Donohue give firsthand accounts of what it takes to blast a city's arteries into being.

Geoff West discovered a trick biology plays to allow organisms to grow--a scaling law that makes bigger animals more efficient. And then he and Luis Bettencourt realized that cities work in kind of the same way--the bigger the city, the more efficient its tubes and pipes and cables. But in the case of cities, there's a twist--a twist that raises some big questions about appetite and consumption.