About cities:
To me, cities in an empire are basically like nodes on a spider web. A tightly knit spiderweb allows efficient use of the surface while a few knots of large sticky string defies the purpose of the web (in spider terms). Normally, however, there are nodes which are more important than others, while most are simply there to help cover the surface. I personally tend to try to cover everything and exploit the land as much as possible in a game like this.
While I agree that cities should be unique in their own way and that bigger cities are better for everyone, I think the way a city evolves has been forgotten. In the first stage of conquest, when you start a game, the goal is to establish yourself as firmly as possible as fast as possible. The location of the first city is often crucial to a lot of the aspects of the game later on, because they usually define the resources available for growth. But once that first city is set, the second stage of conquest begins. In terms of philosophy, it has always been consolidation. When the advantages of expanding outweigh the benefits of improving the starting city, it is obvious everyone will expand in the most efficient way possible. Including city spamming. In our world, many factors prevent humans from gratuitous city spamming, the foremost being limited resources. If the cost of spawning new cities is negligible, new ways must be devised.
If bigger cities are more profitable, by providing some kind of synergy bonus (an advantage due to increased size), it will become a very profitable long term investment to spawn as many small cities as possible to eventually get as many big ones as possible. Especially if small cities grow faster. Which means that spawning cities must be limited either logistically or economically or both. I personally don't see how it would make the game more fun to limit spawning so much that the user will just have to end up with 5 cities that produce everything, each one specializing in its own domain, especially if those large cities are fairly easy to loose.
We all know in general, a city has its growth phases. In the first phase, the town basically can only produce raw goods. There is few people, they are having trouble surviving and need the protection of a bigger city if they ever hope to flourish. Then, as the town grows, more services are provided to the population which starts to look down upon menial tasks such as "farming", and "sowing". Which in turns means they require more than they produce, in exchange for more advanced production. Of course, this would mean that each capital city would need a bunch of small villages to provide for it the resources it needs to be grand. And the user would also need to limit growth to those villages for fear of lacking resources. And that's not fun either.
So there are very few ways one could hope to have only a few large cities and be content. First, logistics need to be considered. If resources are acquired exclusively through population, the population cap of each city should never be reached, because sooner or later, the user will want more cities. And if resources are acquired through buildings, and that amount of space is fixed, there simply isn't any viable solution to keep the number of cities at a respectable level. Having that amount of space vary in relation to city level would help alleviate that, but sooner or later, the user will want more cities. And if the short-term tradeoff for founding a new city is too low, spammage will be on the way. So resources obviously need to be generated by something other than cities directly. It could be population, as people suggest, or area of influence or both, preferably. Meaning the user would still have to expand physically, which he would. And if the most efficient mode of expansion is something other than building cities, that's exactly what he'll do.
Growth in small cities should be very limited. The concept of area of influence would also need to be revised, because users like me will want to use and abuse all of the map surface. Meaning those 5 cities would need to allow total map control. Obviously, there could be "influence nodes" which could provide influence over large and distant areas cheaply and efficiently. They would have to allow troop movement, too, maybe something like a nydus canal. This is needed to prevent using cities to accomplish that same goal. Simply crippling city spawning is just a way to reduce fun. While having the establishment of a new city become a major event (in terms of cost and planning) is what I think FrogBoy is looking for.
Growth should be favored in large cities. Too often do we see an arbitrary population cap at which point the user, wanting more growth, has no choice but to settle more. By anticipating this and accepting a harder start of games, most megalomaniac users will spam as much cities as they can, always trying to optimize long term growth. On the other hand, if there are no caps, there is no reason for the user to have more than one city other than good production, and that defies the purpose of cities. By putting a limit on production based on area of influence (say 100 population per tile), we can remove the desire for new cities in terms of growth. They could and should contribute to area of influence, but other cheaper means should be provided to allow user to increase their area of influence. Also, limits to what you can sustain should be dependent on area of influence and/or money, but preferably both. As in free upkeep based on area of influence. By making economics and many other aspects of the game dependent on area of influence, we insure motivation for physical expansion and physical protection. We also insure that cities won't be spammed as they don't provide any real bonus just by being there. Ultimately, the user could choose to only have 1 capital city, to specialize in whatever he wants to specialize, and still be competitive, but not as versatile as someone who has 2 or more. If the specializations are limited (say 5 city types), so are the efficient cities.
Here is a bullet point summary:
- Turn major cities into hubs that could do anything, but can do only a few things well. Have them be self-sufficient, unlimited population growth centers. Capturing one should be a very hard blow to your enemy.
- Make small cities be a major and risky investment. Growth and profit should not be generated from these. Capturing one should also be very expensive. Only immensely rich users could ever hope to sustain two at once. (This point needs factoring from something like (total_city_level + (city_count - 1) * 5)). Meaning the first city could be really cheap to expand while the second one could really put a dent in your economics.
- Provide an alternate method of expanding area of influence (other than cities).
- Make area of influence something like a resource. If there are limits to be set (population, buildings, troop count, whatever), they should depend on this. This would be the equivalent of upkeep.
- Remove resource production buildings as they are the best incentive to spawn new cities. Make resource production dependent on population and/or area of influence.
- Make sure the only interest a user might have in a city is what it can specialize itself into. Also make sure redundancy is useless other than in terms of safety.
So basically, the point is this: allow the user to do all that more cities allows him to do, but without cities. Then you'll be done for good with city spamming.