In the essay Aesthetics of Urban Design it is argued that contemporary aesthetics should have a base in the design of the city. It is in the everyday life of the city that people can train, exercise, improve and enlarge their aesthetic sensibilities. Given this context, two different approaches have to be distinguished. On one hand Lewis Mumford praised the medieval city as leading to the “dilation of the senses”. This is the historical approach to the question. On the other hand, however, urban design could play an important role in reconstructing the aesthetic sensibility especially today. Different reasons are relevant here. Since we can’ t presuppose that in the time after postmodernity people easily find access to the aesthetics, urban life could function as a new beginning. City life in many ways makes us acquainted with the aesthetic. The architecture of the houses, the layout of the street pattern or the atmospheres of a square have to be mentioned here. The relevance of urban design for the foundation of aesthetics can in different ways be argued from pragmatism’ s connecting the art more closely with the everyday life. John Dewey did so. But also neo-Marxism’ s idea of “sublating” art by realizing its promises in everyday life is relevant here. The essay argues that the slums, which are to be found all over the world sets some limits to the thesis that aesthetics, today, originates from urban design.