Italian Renaissance architect Sebastiano Serlio (c. 1475-1555), who began to work as an architect only in his maturity and in France, is known and appreciated chiefly as a theorist and author of the highly influential treatise L'Architettura. This important publication is the first to document Serlio's work both as a theorist and builder. It traces the overall evolution of Serlio's production in relation to his time, commencing with a detailed analysis of the chateau of Ancy-le-Franc, in which the two fundamental components of his formal language are already apparent: his Italian training in the classical manner and the profound influence of the French emphasis on decoration. This book reconstructs the specific features and overall evolution of Serlio's career, one in which his activity as a designer and builder played a much greater role than was previously thought. The analysis of buildings and projects is supplemented by frequent references to his treatise and by a chapter on his life that aims to reveal his true personality by stripping away the prejudices that surround it.