What really causes unrest? I mean, does unrest have a chain-ability - does it spread from town to town. Cos' I'm playing Seleucids, and even in 190 BC, Ecbatana, Apameia, Hecatompylos, Asaak and Zadrakata all SUDDENLY go red with unrest, even though they have been happy for the last three decades??? One of them could be explained by the death of a nice governor, but all of them? Hardly... Also, Ecbatana once simply REVOLTED with no warning - no previous turns of ordinary riots. Now it may have been in the red for a few turns (ruling from Cyrene to Gava-Haomavarge on a slow computer, you don't check every city every turn, but merely fix the rioting ones), but it definently HADN'T been rioting - it just SUDDENLY expelled my garrison - and that despite being a province I had had all game long, posseissing a rather large garrison and being located much closer to my capitol than cities like Gava-Haomavarga, Chach and Axum, all of which remained perfectly obedient.
So for some reason 'unrest' just suddenly flares up in the middle of your empire. Now all other complaints (cultural penalty, distance to capitol, etc.) I can see the explanation for, just like unrest in newly conquered places makes sense. But is unrest within your boundaries just completely random or is there some reason why a city like Ecbatana just gets 80% unrest out of the blue (of course, it might have gotten it over a few turns, seeing as I didn't keep an eye on it, but WHY did it get it)?