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.

There are two ways you encounter things in the world that are different. One is everything that comes in reinforces what you already believe and everything that you know. The other thing is that you stay flexible enough or curious enough and maybe unsure of yourself enough, or may be you are more sure of yourself - I don't know which it is - that the new things that come in keep reforming your world view.

To seek "causes" of poverty in this way is to enter an intellectual dead end because poverty has no causes. Only prosperity has causes.

As in the pseudoscience of bloodletting, just so in the pseudoscience of city rebuilding and planning, years of learning and a plethora of subtle and complicated dogma have arisen on a foundation of nonsense.

The second mode to deal with unsafe cities is to take refuge in vehicles. This is the technique practiced in the big wild-animal reservations of Africa, where tourists are warned to leave their cars under no circumstances until they reach a lodge. It is also the technique practiced in Los Angeles.

...frequent streets and short blocks are valuable because of the fabric of intricate cross-use that they permit among the users of a city neighbouhood.

While you are looking, you might as well also listen, linger and think about what you see.