A term of comparatively recent origin, though a phenomenon of great antiquity, “the built environment” generally refers to those elements of the physical environment that are constructed by and for human activity. The built environment might thus include not only structures and sites such as buildings, roads, bridges, parks, and playgrounds but also (and more broadly) land-use patterns, transportation systems, architecture, and design (Saelens and Handy 2008; Bartuska 2007). Closely identified with cities but not exclusively urban, and often regarded in the modern era as separate from or even opposed to the “natural” environment—epitomized by Lewis Mumford’s formulation, “As the pavement spreads, nature is pushed farther away” (Mumford 1938)—the built environment did not figure prominently in early currents of environmentalism either in the United States or globally. In the last decades of the twentieth century, however, theorists and practitioners alike began to question this absence. “Why is it that we tend to think of the built environment of cities as somehow or other not being the environment?” asked geographer David Harvey in the late 1990s. “There is, it seems to me, nothing particularly anti-ecological about cities. Why should we think of them that way?” (Harvey 1997).