A complete and authoritative resource for professionals and students on a subject of essential interest for all in the world of architecture. The design of imaginary, conceptual, or radical buildings is as old as the practice of architecture itself. For centuries architects have drawn on their creative abilities to produce breathtaking works of architectural imagination. At no period has the investigation of new spatial forms been as rich as from the Second World War to the present. With such historical precursors as Piranesi and Ledoux, and, in the twentieth century, Melnikov, Sant'Elia, and others, architects have created an astonishing range of architectural constructs and urban utopias that have influenced generations of architects. This publication contains three parts: a thematic overview of the most important and far-reaching work created since 1945; a survey of contemporary visionary architecture, particularly in the digital realm; and an illustrated lexicon of ideas, movements, people, and terms. The early, unbuilt world of many of today's most important architects--Daniel Libeskind, Rem Koolhaas, Peter Eisenman, Zaha Hadid, Bernard Tschumi--is represented alongside the seminal work of earlier practitioners, such as Archigram, Archizoom, and Buckminster Fuller. Recent work is explored in case studies of contemporary visionaries, including Diller+Scofidio, Asymptote, Morphosis, and NOX. 500 illustrations, 250 in color.