Caesar III makes the most of its artificial constraints in order to make each subsequent level a bit more complex, but it's a fun system. Pleasing your populace requires schools, theaters, libraries, bathhouses, and the like. Many of these complexes can't be built too near housing or the neighborhood won't reach the most desirable class levels. Of course, pleasing the populace also requires food, and lots of it. This is the area in which Caesar III is both the most demanding and, sometimes, the most confounding.
Food is stored in granaries.
Market collectors go to these granaries and then distribute the food to the people. Unfortunately, collectors often don't go to the closest granaries. On many occasions, market traders will pass through granaries stocked with a variety of food, only to go take food from another granary located far away. All the while, the people are starving. It's frustrating, especially when you're trying to reach a particular prosperity level, your granaries are brimming, and yet your people are starving.