Amphitheater at Pompeii

Note the imposing ramps giving access to this amphitheater.  Although it may not be clear in this image, there is a riot going on between the townspeople of Pompeii and neighboring Nuceria.  Rivalry between towns could be fierce.  Similarly in modern times, antagonism between factions at  soccer matches has resulted in rioting in Britain and elsewhere.

Here is Tacitus' account of the Pompeian disturbance (Ann. 14.17):

About the same time a trifling beginning led to frightening bloodshed between the inhabitants of Nuceria and Pompeii, at a gladiatorial show exhibited by Livineius Regulus, who had been, as I have related, expelled from the Senate.  With the unruly spirit of townsfolk, they began with abusive language of each other; then they took up stones and at last weapons, the advantage resting with the populace of Pompeii, where the show was being exhibited.  And so there were brought to Rome a number of the people of Nuceria, with their bodies mutilated by wounds, and many lamented the deaths of children or of parents.  The emperor entrusted the trial of the case to the Senate, and the Senate to the consuls, and then again the matter being referred back to the Senators, the inhabitants of Pompeii were forbidden to have any such public gathering for ten years, and all associations they had formed in defiance of the laws were dissolved.  Livienius and the others who had excited the disturbance, were punished with exile (Church and Brodribb translation).

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