In the book, you make a distinction between the complicated and the complex. What systems in cities do you think demonstrate that today?
When something is complicated, it is intricate but often lacks the dynamics that makes a system hard to understand. On the other hand, a complex system implies feedback, a sensitive dependence on the initial conditions, and emergent phenomena that are hard to predict.
At the level of urban infrastructure, we can see evidence of complex systems when things go wrong. When a water main breaks and vast portions of a city’s population receive water from a backup system (and have to boil their water, just in case), or when an outage can cause a city to be without power, we see the sensitivity of a city’s infrastructure and the vast complex system that operates for its population, which most of us are normally blissfully unaware of. Similarly, transportation networks, from a subway to the road networks, are also complex technological constructions that are difficult to fully grasp.