The Citadel is an archive of information for George R.R. Martin's A Song of Ice and Fire.
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I read a lot of history, and mine it for good stuff, but I also like to mix and match. That is to say, I don't do straight one-for-one transplants, as some authors do, so you can't really say that X in Westeros equals Y in real life. More often X in Westeros equals Y and Z in real life, with squidges of Q, L, and A.
In the case of Dorne, yes, Wales was definitely an influence, for all the reasons you cite. But there's also some distinctly unWelsh elements down there. South of the wall of mountains you have a hot, dry country more like Spain or Palestine than the cool green valleys of Wales, with most of the settlements along the seacoast and in few great river basins. And you also have the flavor given the culture by the great Rhoynar influx led by Nymeria. I suppose the closest real life equivilent to that would be the Moorish influence in parts of Spain. So you could say Dorne is Wales mixed with Spain and Palestine with some entirely imaginary influences mixed in. Or you could just say it's Dorne....
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