In a lecture organized by IAUUSP, the author of the celebrated "The Construction Site and the Drawing," Sérgio Ferro, analyzes his trajectory of over 50 years as an architect, artist, and intellectual, from his education to his most recent works. Averse to the separation between theory and practice, his seemingly distinct objects of study help us understand his obstinacy for the place of free work in production. From sophisticated works of art to humble workers' houses, every construction can be read as a historical document, capable of revealing hidden aspects of the men and societies that created them.