Rarely has an architect caused as much sensation outside of the architecture community as REM Koolhaas. His outstanding creations - such as the Dutch Embassy in Berlin, the Seattle Library and the Casa da Musica concert hall in Porto - are working examples of the Dutchman's visionary theories about architecture and urban society. But Koolhaas' work is as much about ideas as it is about constructing buildings; he is equally celebrated as a writer and social commentator. For Koolhaas, what is esse