"Everyone is aware that tremendous numbers of people concentrate in city downtowns and that, if they did not, there would be no downtown to amount to anything--certainly not one with much downtown diversity."

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I have been dwelling upon downtowns. This is not because mixtures of primary uses are unneeded elsewhere in cities. On the contrary they are needed, and the success of mixtures downtown (on in the most intensive portions of cities, whatever they are called) is related to the mixture possible in other part of cities.

— Jane Jacobs