This lecture explores the challenges of urban development, focusing on the impact of post-war housing crises, economic growth, and demographic changes on cities like Lausanne, Neuchâtel, Fribourg, and Sion. It delves into the history of urban planning, the rise of modern urban principles, and the implications of high-rise apartment living. The speaker discusses the construction methods used in modern urban projects, such as prefabrication, and the social implications of large housing complexes. The lecture also addresses issues of social exclusion, safety concerns, and the importance of community engagement in creating cohesive urban environments.