Explore the fascinating world of geometry in this 55-minute lecture from the Fields Institute, delving into the life and work of Donald Coxeter, the renowned mathematician who revolutionized the field. Discover the foundations of Euclidean geometry and its five postulates before venturing into non-Euclidean realms, including spherical/elliptical and hyperbolic geometries. Uncover Coxeter's collaborations with artist M.C. Escher and his groundbreaking work on the fourth dimension. Learn about Borromean rings and the unexpected connection between geometry and music. Gain insight into why Coxeter is hailed as "The Man Who Saved Geometry" and appreciate his lasting impact on mathematical understanding.