Overwhelmed, with sieges.

[BurningEGO]

Unrest that stays around for a long time is almost always caused by enemy spies in your city. Build a spy of your own and if possible stick a general with +to public security in the settlement. You should 'catch' the spy in a few turns. Sometimes huge unrest can be caused from multiple spies. just wait it out, eventually your spy will get rid of all the enemy spies, or at the very least make it harder for them to get more into the city.

Its impossible to be spies in all the cases. I have placed in cities spies (for years) with excelent skill and nothing was found. In certain cases, like islands, its also impossible to be spies.

100th post, yay!