ABSTRACT
From a technological point of view, what is unique about cities is that they are dense concentrations of infrastructure. In the core of most cities, the infrastructure of roads, buildings, and parking lots visually dominates the landscape, to the near complete exclusion of the natural environment. Housing and transporting a large urban population involves the construction of massive buildings, bridges, tunnels, and other civil engineering works. A dense tangle of infrastructure is embedded within these massive structures, extending deep underground as well as high above the streets.
