Interacting with the cities seems to feel a bit combersome. I feel I can't access the information I want at a quick glance and doing stuff takes more clicks then it really should.
The action/resource/training/building tabs seem a bit more then is really needed. All of the information could be just as easily access with 1 main tab and some minor changes to the buttons already there. To better illustrate this I did a bit of editing to some screenshots to show the changes I'm about to suggest and why they could help improve the interface.
Display what's being built/trained on main tab
As you can see the Build and train icons have been replaced by what is currently under production. It's nice that the city blacks out on the Empire tree so you know it is building something but sometimes you wanna know how long until it's finished or what's under construction. But to do that you have to make 2 clicks, one on the city the other on the building tab. The same applies to troops which could be real important to check time remaining during a war but having to click twice to check is a pain.
Click on them would do pretty much what the current buttons there do by opening the train/build tabs and menus. But the main thing is getting the information to the player as quickly as possible. The tabs are already a bit redundant since those build/train buttons already take you to the same place.
Display stack if multiple items being built/trained on main tab
To help given even more information to the player this example shows a stack on the building icon spot to represent there is more then one item in the queue. This way again the player can see quickly if this item is the only one or if there are several others after it. It is more likely to be useful information when it comes to queuing up training for lots of troops.
As for the resources tab I think all that information could go directly into the city details book. It seems a bit sparse right now with plenty of room for expansion. But with that there would not be the need for the tabs and you'd simply click on the buttons to access all the info/menus that are in the tabs.
Display turns until pop cap or city level up
It would also be nice to have it show how many turns until you reach population cap or city level up. Again this just makes it easy for the player to get this information. Otherwise they have to look at the tool tip over the bar or the city details and figure it out themselves.
Personally I like to make my city run as efficiently as possible. So if it takes a house 3 turns to build then I don't wanna start building the next one until I'm 3 turns from population cap. There is no point in having lots of empty houses around when I could have production buildings up and running first. But I constantly have to figure out how many turns until I reach population cap and it becomes tedious micromanagement as the game progresses.
Conclusion
Most of this stuff doesn't seem so bad on small maps with few citys but once your city count nears double digits this stuff really wieghs down the game and kills the momentium. It ends up making the late game feel very tedious have to look in different tabs and tooltips for information that should be readily available.
