This lecture discusses the evolution of architecture during the late 18th and early 19th centuries, focusing on the works of key architects such as Etienne-Louis Boullée, Claude-Nicolas Ledoux, Jean-Nicolas-Louis Durand, Karl Friedrich Schinkel, and Henri Labrouste. The instructor highlights how these architects responded to the growing importance of construction and engineering, emphasizing the rationalization and simplification of architectural forms. The lecture explores the shift from traditional classical orders to a more functional approach, where architecture began to serve new public programs like museums and stock exchanges. The role of the state as a client in architectural commissions is also examined, marking a significant change in the relationship between architects and their patrons. The discussion includes notable projects, such as Boullée's library design and Ledoux's saltworks, illustrating how these architects navigated the challenges of their time while contributing to the development of modern architectural principles. The lecture concludes with reflections on the impact of these historical figures on contemporary architecture.