Few designed works—whether a building, a stage set, or a piece of furniture—would ever have seen the light of day if not for drawing’s capacity to generate, refine, and share artistic ideas. Many surviving drawings from eighteenth-century France served exactly this purpose: to envision and describe an architectural, sculptural, or decorative object, often with the intent to convince a patron to go forward with a proposed commission. Some drawings document works that have since been lost, damaged, or destroyed, giving them inestimable historical value; others record ideas for designs that were never realized but still offer precious insight into an artist’s creative powers. This is the case with drawings by Jean-Jacques Lequeu and Étienne-Louis Boullée, for whom paper was a vital support on which to imagine monuments to their philosophical ideals; on the page, they were unfettered by the material constraints of a real building project. Both architects donated their drawn archives to the BnF to preserve their visions for posterity.