Agglomeration and Economic Theory -- Cities: Past and Future -- Why Do We Observe Agglomerations? -- On the Relationship between Space and Economics -- Plan of the Book -- Fundamentals of Geographical Economics -- The Breakdown of the Price Mechanism in a Spatial Economy -- The Quadratic Assignment Problem -- The Spatial Impossibility Theorem -- The First Welfare Theorem in a Spatial Economy -- Considerations on the Second Welfare Theorem in a Spatial Economy -- The Thunen Model and Land Rent Formation -- The Location of Divisible Activities -- The Urban Land Rent -- Increasing Returns and Transport Costs: The Fundamental Trade-Off of a Spatial Economy -- Microfoundations of Increasing Returns at the City Level -- City Size under Scale Economies -- Trade in a System of Cities -- Competition and the Spatial Organization of Markets -- Cities and the Public Sector -- The City as a Public Good -- The Number and Size of Cities under Politics -- The Structure of Metropolitan Areas -- The Spatial Structure of Cities under Communications Externalities -- Agglomeration as Spatial Interaction among Individuals or Firms -- The City as Spatial Interdependence between Firms and Workers -- The Monocentric City -- The Polycentric City -- Suburbanization and the Location of Multiunit Firms -- The Formation of Urban Centers under Imperfect Competition -- Monopolistic Competition and the Formation of Shopping Districts -- Oligopolistic Competition and the Agglomeration of Retailers -- Consumers' Search and the Clustering of Shops.