Corrected entry: After the battle against the Germans, Maximus lets out a cry of victory: "Roma victor." This is supposed to be Latin, but, they got the grammar all wrong. "Roma" is feminine, so it should be "Roma victrix". Amazing how a mistake is still possible as there are only about three sentences in Latin in the entire movie and a lot of specialists were supposed to have been working on it.
Corrected entry: While in his tent, Marcus Aurelius shows Maximus a sword with the inscription "MARCUS AURELIUS FECIT" (Marcus Aurelius made [this]). The Roman alphabet did not include the letter U until the Middle Ages; V was used instead. Moreover, Latin text did had neither spacing nor punctuation. Thus, the inscription should have read "MARCVSAVRELIVSFECIT".
Corrected entry: In the first battle scene against the Germanians, right after Maximus gets dismounted, he is lying on his back and an enemy soldier takes a swing at him with an axe. Maximus blocks it by holding the sword handle with his right hand and putting his left hand on the top of his sword blade. With the amount of force the axe came down with, blocking like that would surely cut off one's own hand.
Corrected entry: During the "Battle Of Carthage" fight in the arena when Maximum gallops past Juba on horseback, Juba shouts "Maximus!" and throws him a sword which Maximus goes to catch. But if you watch closely right at the end of the shot you can see Maximus' hand fumbles and doesn't actually manage to catch the sword - yet in the following shots he is still riding around the area, wielding the sword.
Corrected entry: At the start of the first battle when we see Maximus riding on a horse, he comes across a Germanian about to stab a soldier. He rides along and cuts the guy's hand off. If you slow this part down, it's not blood that comes out the wound but what looks like bits of wood.
Corrected entry: The forest in the opening battle scenes is man-made and not the natural, wild forest that would have covered Germania at this time. The trees are all in nice straight lines, there are no low hanging branches and no tangled growth on the forest floor. If this were a natural forest the Roman cavalry would not be able to gallop through it and weave effortlessly between the trees as is depicted.
Corrected entry: In the scenes of the Colosseum the shade of the arena is wrong. There would be two types of tickets: shade or sun. One half of the Colosseum would be shade and the other sun. This is still practiced in Spain at bullfights. The shade tickets are much more expensive of course. In the movie it looks more like closer to noon than four or five o'clock.
Corrected entry: Cicero lived at the same time as Julius Caesar (the 1st century BC), not during the 2nd century AD as the film claims.