This thesis investigates the geometry of the ribbed dome of San Lorenzo Church in Torino, a masterpiece by Guarino Guarini. The church is renowned for its structural innovation, its proportions, and use of light to ma-nipulate vision, making the dome appear higher through its repeated pattern. The study begins with a general historical overview of Guarini's background, detailing his architectural projects and treatises, and placing his work within the broader context of Baroque architecture. Following this, the thesis delves into the history and architecture of San Lorenzo Church, with a specific focus on the main ribbed dome. It incorporates debates and discussions from eminent researchers such as Professor Susan Klaiber, Henry Millon, Elwin Clark Robison, and other scholars, whose work significantly influenced this study.