Nowadays, it's quite how surprisingly similar how similar modern cities are. Not only are cities and buildings similar, but so are the slums that surround them (in the first world).
How much of this is a product of fashion (imitation of international cnstruction style) and how much is a result of the materials and building techniques existant in this stage of technological development??? Would all societies who have reached our level of technology build more or less in the same way??? Or would cities in a world in which the industrial revolution had first taken place in China or in Persia be radically different from our own??? If so, how?