This book examines the history, theory and practice of parallel (orthographic) and central (perspective) projection. The objective is to provide the tools to imagine and represent with precision, dexterity, and virtuosity, a continually expanding repertoire of three-dimensional architectural form. The focus is twofold: first, to trace key historical developments of projection in architecture from the Renaissance through the Enlightenment into the twentieth century and second, to explain the comprehensive codification of Descriptive Geometry as defined by Gaspard Monge at the end of the eighteenth century and the means by which it is practiced. The projective systems of Girard Desargues and Monge are revealed to have altered contemporaneous relationships between masons, carpenters, engineers, mathematicians, cartographers, painters and architects.