I don't know about rare resources for horses... I started a new game, and a dozen or so squares from my first settlement that I founded, I discovered some wild horses... Lucky find.
That and my first town had 2 gold mines near it, 2 iron mines, 2 fertile land, lumber, ancient library and temple of arcane
I was like "Oooooooh yeeeeeeeah". Granted, the gold mines are a little far out and I still need 1 more level for my town before I get 'em, but still... talk about super location.