CHIME NOISES INTENSIFY
My guess is the first places that were settled were places near water, as they most often are in real life. So Relic Castle, (keep in mind, no desert/it IS near water) Castelia City, and Driftveil. (definitely Driftveil since we learned that klink appeared about a hundred years ago, and someone had to notice that?) Also, maybe even opelucid, since it is very old looking in white, and perhaps Icirrus because of the architecture?
Also, definitely the East side of Unova. Landorus's shrine, the ruins, Lacunosa town... it all screams ancient civilization.