Nijkamp, Peter2013-07-262013-07-262009-12http://hdl.handle.net/10400.1/2824Cities are the seedbeds for creativeness, innovation and spatial competitiveness. They are characterized by product heterogeneity and behave according to the laws of monopolistic competition in economics (see Frenken et al. 2007). Modern cities try to offer the highest possible quality or image in terms of culture, arts, sports, innovativeness, entrepreneurship, financial markets, sustainability etc. Density and proximity are the key features of modern cities (or, in general, urban areas). The past centuries have been characterized by a structural trend towards urbanization. Some 200 years ago less than 20 percent of the world population lived in cities, whereas nowadays the urbanization degree is moving towards 80 percent. Not only has the number of cities increased rapidly, but also the size of cities.engbook part