Factual error: Women were not allowed to be mixed with men. Only Vestales could stay where men were. Women could see the games just from the last ring-level of the Colosseum.
Factual error: Early in the film Maximus walks through a cereal crop trailing his hands against the heads of grain. Except that dwarf varieties of cereal were only bred in the 20th century. Before this a crop would have been up to a man's shoulders.
Suggested correction: No doubt the scene was shot with a modern variety, but it turns out that it is a good approximation of the wheat grown at the time of the story. Two varieties of wheat grown in ancient Rome, the Emmer and Eikorn varieties, reach only 2-3 feet at maturity. These were originally wild wheats that had been cultivated for 8-10 thousand years BCE.
Suggested correction: This movie is not based upon facts. Many element were fictionalized. This is just example of fictionalized things.