1. Smithy - during the Middle Ages, this made a big difference

2. Ironworks - during the Renaissance, this is what made England, France and Northern Italy the military powerhouses of the continent. Cannon production was based on huge royal ironworks.

It makes no sense that agriculture continually improves (through the granary and terrain improvements) while industry stays essentially the same until the 18th century factory comes along. I know that mines are supposed to do this, but the gap stills seems too huge, and you can't devote all your city squares to mines or the people will starve.