Having territory within your borders will brighten up and reinvigorate the land, having a chance (depending on the terrain, not a random roll) to boost the natural resources and give more food.
There is a certain spell you can cast within the game.
Before the game, you can try to choose the different maptypes, I think temperate should give the best chances for city locations.
Also if you have plenty of time you can make custom map stamps with the workshop, but thats more like a "modding" option 
I think there was a map mod though, hmmm
Found this, dunno if its working: https://forums.elementalgame.com/433981
Sincerely
~ Kongdej