1In a standard textbook on urban economics by Mills, Hamilton (1994), the authors raise the question: ‘What are urban areas?’. They argue that there are many urban concepts: town, city, urban area, metropolitan area, and the like. Some of these concepts are based on legal definitions, and hence these definitions vary across nations. Others are based on population figures and reflect the fact that in urban areas the average population density is higher than elsewhere. The authors provide the following basic description: ‘Thus the fundamental and generic definition of an urban area, or metropolitan area, is a place with a much higher population density than elsewhere’ (p. 3). It is thus apparent that the concept ‘urban’ is not a clearly operational term. In our study, we use this term as a general description of a place or area with a relatively high concentration of people in a demarcated built environment. To be slightly more precise, in the present study, we adopt the following nomenclature in the present paper (see the Dictionary of Human Geography, edited by Gregory et al. (2009)):