Revealing mistake: In the beginning of the film at the major fight sequence. When you see the Romans shield themselves with the rectangular shields against the barbarian's arrows and then they charge at each other. If you look closely enough, you can see two Roman soldiers standing there having a great laugh, one pointing a sword smiling, and the other one staring at the ground laughing to his heart's delight. (00:09:15)
Revealing mistake: After the first battle in the Colosseum (The Battle of Carthage), Commodus decides to meet "The Spaniard" in the arena. When Quintus (the head of the Praetorian Guard) is telling the slaves to drop their weapons, we can see one of the spectators hiding a plastic bottle of water (right upper corner of the screen). (01:25:58)
Revealing mistake: As Tigris lays injured on the floor of the Colosseum, there are several close-ups of Maximus holding the axe above his head, with light streaming in around him. There are two things wrong with this; First of all, the camera angle is nowhere near steep enough to see the top of the Colesseum, therefore no light rays. Secondly, the top of the set can actually be seen between the light rays, as the canvas shades are too short and wide to be those seen in the CG wide-shots. Use the DVD "Making Of" as reference. (01:43:20)
Revealing mistake: In the scene where the Praetorians attacks the gladiator's quarters and the gladiators are forced to fight in order to hide Maximus' escape, Hagen is shot full of arrows. Note the blocky silhouette of his torso area? What kind of padding is he wearing under that canvas jerkin? (02:07:10)
Revealing mistake: When the chariot crashes in to the gladiators, we can see the shield in which the chariot crashes in to. It's not shaped like the other shields which are shaped in a perfect bow. This shield is rectangular shaped most likely to balance better on what ever is supporting it when the chariot runs over it making the chariot tip over. (01:30:00)
Revealing mistake: In the "Battle of Cartage" when the first of the chariots is turned over, right after Maximus is saying "Hold, hold...down low, down low," there is a series of shots to the crowd, there is a bearded man celebrating with both arms, and deep to his right (left on the screen) there's another man, wearing some kind of clothes with stripes black and white. Behind him, there is an old man who appears very briefly, and he's wearing glasses. (01:25:50)
Revealing mistake: During the gladiator battle where Maximus is fighting gladiators alone, there is a particular shot with the gladiator he recently sliced up the stomach on. First Maximus hits him in the face, and you can see blood gutter up from the ground instead of from his face. Then when it cuts to Maximus stabbing him, blood gutters from behind Maximus, when in fact the gladiator is standing in front of him. (01:04:20)
Revealing mistake: In the Moroccan prison the iron bars are electric arc welded. As a blacksmith, I can easily spot the visual differences between electric arc welding (a modern technique) and pierced bar joinery such as the Romans would have used.