This is a painting that was found in one of the houses of Pompeii. It is a very accurate depiction of the amphitheater at Pompeii. Note the two staircases that lead up into the amphitheater, the temporary sales stands in front of the stairs, its oval shape, the canopy over the seating area, and in the interior the tiered seating. On the right side, the square structure with the pool in the center is the large palestra (exercise area)—that still exists. On the near wall of the Palestra, the Latin inscription announced games that were put on by a Lucretius and his son prior to the event depicted in the image.
The event that is depicted is a riot that occurred during the games in A.D. 59. This event is known from historical sources and it was between the residents of Pompeii and those of nearby city of Nuceria. Notice all the people with raised arms = fighting—both inside and outside of the amphitheater. Note that the lower elite seating area has been vacated, but there is fighting in the upper portion of the amphitheater where the lower classes sat.