@Blhurr:
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Your forgot to insert always a 'U.S.' (= cities located in the United States) in front of the (word) cities.
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Cities are generally built on flat ground but they don't have to be, especially in the future where engineers have devised all kinds of means of building on oddly angled surfaces.
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Depends. In flat regions in the past centuries cities where often founded on hills because of the better defensive abilities.
(Just watch pics of old cities in Italy, most of them founded on hills with a castle/fortress on top of it/the center of the city)
Or they had been founded in river deltas for the water supply. (nearly all of todays major cities)
And it always depends on the landscape of the country and for sure the historical background.
-> in countries like Switzerland they had been founded in valleys (made by a river).