It's interesting. Took me a few tries to grasp it. Another kingdom was able to get past my line with an outpost and fill up the spots I'd been saving, so I had to set the other side of the map on fire to get barely enough room to build a park for the win. I started getting in the habit of filling my empty spaces with gems so that no one could take them. But because of this I wasn't really able to convert my farms and ateliers to cities. I find planning ahead what to put where to be pretty daunting, especially since the requirement for cities is a very exact number of buildings. It might be nice to be able to build over your own structures as your needs change.