India, Oct. 20 -- On a humid evening in Bengaluru, a stretch of road clears itself of traffic without a single policeman intervening. Sensors beneath the ground detect congestion forming a kilometre away and reroute vehicles before the jam materialises. In Surat, a water grid predicts leaks hours before a drop is lost. These are not glimpses of a distant future; they are signs of how Indian cities are beginning to evolve into thinking systems.

Before the end of this century, the most powerful and complex form of intelligence on Earth may not be biological or robotic. It will not walk or breathe. It will be something larger and more diffuse: our cities. What were once physical spaces for human activity are becoming living networks that se...