European cities are centres of finance and commerce; centres of culture, knowledge and creativity; centres of communication, power and influence as well as visitor and tourist centres. The concentration of people and business activity has many benefits that make locating in the city worthwhile. Agglomeration is a dynamic process, cities are not static areas. Indeed, urban size and variation are precisely what makes change possible. This project is an economically focussed study looking at the process of agglomeration within city regions across Europe, i.e. areas which are typically NUTS2 regions and which contain a primary central city. The analysis will contribute to creating a better understanding of and to suggesting optimum scales for urban form and agglomeration, taking into account both the economic costs and benefits of large urban agglomerations.