This book presents a selection of papers from the International Conference Geometrias'17, which was hosted by the Department of Architecture at the University of Coimbra from 16 to 18 June 2017. The Geometrias conferences, organized by Aproged (the Portuguese Geometry and Drawing Teachers' Association), foster debate and exchange on practical and theoretical research in mathematics, architecture, the arts, engineering, and related fields. Geometrias'17, with the leitmotif "Thinking, Drawing, Modelling", brought together a group of recognized experts to discuss the importance of geometric literacy and the science of representation for the development of scientific and technological research and professional practices. The 12 peer-reviewed papers gathered here show how geometry, drawing, stereotomy, and the science of representation are still at the core of every act leading to the conception and materialization of form, and highlight their continuing relevance for scholars and professionals in the fields of architecture, engineering, and applied mathematics.