It should be pure math to determine the absolute maximum shields/turn/city number. Like you just counted the maximum number of people in one city.
Let's see... The city should be able to support exactly 20 inhabitants, no more, no less. That would require four maximum food production squares as the hills produce on food each but as many shields as a mountain (7: Mined, railroaded & coaled). Makes 16 hills with railroads and coal -> 6 shields each. One hill with iron, as we need the Iron Works. So without any city improvements we get 16*6+5=101.
Then a nuclear plant: 2*101=202 and the Iron Works: 2*202=
404
If you still add the mobilization the number comes up to 472.
It's still possible to lower the number of food by four, there is currently "too much" of it, 44. You tell, what kind of square would produce (at least) three foods and as much shields as possible..?
JoseM's Antium is pretty impressive, though.
Still about that Monster Production city... Yet another point that confirms it is modded is that ICBM's cost 600 shields, in this mod they cost <= 524 shields. And the squares produce 8 shields, 7 should be the maximum as I wrote at first. Or did I miss something?
