When did drawing become an integral part of architecture? Among several architects and artists who brought about this change during the Renaissance, Francesco di Giorgio Martini's ideas on drawing recorded in his Trattati di architettura, ingegneria e arte militare (1475-1490) are significant. Francesco suggests that drawing is linked to the architect's imagination and central in conveying images and ideas to others. Starting with the broader edges of Francesco's written work and steadily penetrating into the fantastic world of his drawings, the book examines his singular formulation of the act of drawing and its significance in the context of the Renaissance. The book concludes with speculations on how Francesco's work is relevant to us at the onset of another major shift in architecture caused by the proliferation of digital media.