As elements of the built landscape, works of infrastructure are a means rather than an end. Our cities' rail lines, bridges, highways, waterways and off-ramps are essential in a practical sense, but dead in a social one because they create boundaries that prevent one metropolis from physically connecting with another. Yet their very physical presence reveals hidden qualities key to revitalizing urban life. In Public Natures, New York City-based firm WEISS/MANFREDI tests such possibilities by crafting a hybrid manifesto/ monograph filled with essays, roundtable discussions, and recent projects that explore new opportunities for infrastructure.