Jacobs advocated for "mixed-use" urban development – the integration of different building types and uses, whether residential or commercial, old or new. According to this idea, cities depend on a diversity of buildings, residences, businesses and other non-residential uses, as well as people of different ages using areas at different times of day, to create community vitality. She saw cities as being "organic, spontaneous, and untidy," and views the intermingling of city uses and users as crucial to economic and urban development. [Project for Public Spaces](https://www.pps.org/reference/jjacobs-2/)