One of the nice things about the UI at present is how it uses the "Empire Tree" to highlight Cities or Units that have options to build/move during the present turn.  Once I discovered this, it made managing a larger kingdom much easier.

It bogs down when it starts showing cities that just can't build anything, or cities that have improvements I don't want. 

Often, since I specialize with my city productions, I don't find that I need food improvements in a gold-producing town, for example.  But the city improvement screen always makes the town show up as "buildable" in the "Empire Tree" if I have granaries available and haven't built them in a town.  This means that my "Gold town" will always show up as buildable until I build the granary out of frustration (a total waste of resources).

At the middle to late stage of the game, when I have 10 or more cities, this effectively disables the functionality of this part of the UI, as all of my cities have either built everything or specialized and now have buildings I don't want to build in that specific city that are nevertheless available for building.

At the very least, I think this feature should change to only show cities that have the ability to build further improvements.  Beyond that, I think it would be ideal to only show cities that have useful improvements.  I have three proposals to solve the latter issue, in order of preference:

1) Only allow improvements to be built is they are applicable to the town.  The UI checks to see if, for example, food is produced in the city before it lists food improvements.  If there isn't any food production, then granaries don't even show up in the build queue (or maybe they are grayed out and still selectable, but don't come up as first-choice build options and don't trigger the Empire Tree).

2) Allow the user to lock out improvements on a specific town that she doesn't want to build.  So I don't want a granary?  I have a little lock that I can click, or I can right click and tell it to lock it out, or whatever mechanism would indicate that I don't want to build that improvement in this town.  If I lock out all the choices, the Empire Tree no longer shows that town as "buildable."

3) Allow us to manually mark the town as "inactive until new improvements are available."  So I've built everything I would want at my present tech level, but I want to look again if there's a new improvement available.  Just let me click a box to switch this off until a new tech level allows a new type of building in this city.

Thanks for your time.  Keep up the good work.