Visible crew/equipment: In the "Battle of Carthage" in the Colosseum, one of the chariots is turned over. Once the dust settles you can see a gas cylinder in the back of the chariot.
Factual error: When a group of soldiers goes to Maximus' villa to burn it and kill his family, his son points them, saying in perfect Italian "Mama! I soldati!" I just don't understand why he speaks Italian in a movie in English, where people are supposed to speak Latin, in a province where this language was never ever spoken.
Visible crew/equipment: After the battle with the Germanians, the next morning after the tavern, he is walking in the army camp and he feeds a horse a piece of apple. If you look closely between Maximus and the horse, there is a crewman wearing a pair of blue jeans.
Revealing mistake: After Maximus and Tigris' battle, Tigris falls to the ground and we see his mask is already up. Maximus then pulls the mask up which has magically come down over Tigris' face again.
Factual error: In one of the scenes in Rome leading up to a fight, leaflets are being handed out. These didn't exist, event notices were written up on boards.
Revealing mistake: As Maximus approached his home after he should have been killed, the grain fields clearly show marks which are only caused by a tractor during crop spraying.
Visible crew/equipment: During the first Gladiator match in Morocco, Maximus and Juba are chained together. Once they have killed the last man, the camera takes us around the arena. You can clearly see the shadow of the camera on Maximus' chest. It happens twice.
Continuity mistake: During the enactment of the Battle of Zama, Maximus rides his horse around a bend with his sword in his left hand. When we cut to close up, it's back in his right. Looking at the left-handed shot in freeze-frame, you can see the frame has been flipped, left-to-right (check the armor). This was probably for continuity reasons. Similarly, Maximus jumps on the horse and his shoulder protector is clearly on his injured left shoulder. However, a few frames later, the protector is on his right shoulder, then it moves yet again back the correct spot, the left shoulder.
Revealing mistake: After the final fight scene, where Maximus is dead and on his back in the sand, his armour should have made his head droop horribly backwards. To avoid that, the filming crew put a pillow of sand under his head to raise it about three inches.
Visible crew/equipment: During the scene where Maximus throws the sword into the crowd and yells "are you not entertained," the camera pans around, and in the crowd, for a split second, you can see a cameraman in jeans and a shirt standing next to a camera. This is visible on the big screen, but hard to see on video, unless you see it on DVD and can zoom in.
Other mistake: When Maximus enters the arena before facing Tigris, the camera pans around the crowd. At one point, you can see a young Hispanic girl wearing a "scrunchie" holding her hair in a perfect ponytail, several bracelets and a watch, a necklace, a cut-off white t-shirt, and blue jeans. Most noticeable in full screen version.
Continuity mistake: When Hagen tests Maximus in the sword fighting, watch closely the scene behind them. At the time when Hagen strikes Maximus for the first time you can see gladiator behind taking a glass. At the time of the second strike you can see only a glass. When Hagen stopped his third strike you can see the same gladiator holding a glass and looking around. This time he is turned toward the camera and you can see a red spot on his chest.
Factual error: Before Maximus enters the colliseum, he selects a helmet and places it on his head. On the rack is a copy of a saxon helmet found at Sutton Hoo, England and part of the treasure found at that location. Unfortunately this is a 7th century design.
Factual error: When the execution squad is ready, Quintus says "fire". Of course this is incorrect, since you don't fire a bow and arrow, but "loose" it. The term "fire" came only with the invention of firearms. It's a common mistake in bow / arrow type situations. (Extended version only).
Factual error: The opening battle is wildly inaccurate. The Roman legions were trained to fight as a regimented force, and to maintain formation for mutual support. In the film, the formation collapses instantly upon contact with the enemy; in addition to being inaccurate, this would have almost certainly led to a Roman defeat, as, on a solo basis, the barbarians were by far the better warriors. Further, the Roman legions used spears called pila. Doctrine called for them to be thrown while the enemy closed. The Romans would then draw their swords and fight, while remaining in formation. Though the Romans are shown holding their pila in the opening scenes, they are never used against the barbarians, and we see no pila-riddled shields and/or corpses in the background.
Factual error: At several points in the movie you will see speeches to a large crowd. These take place at the Piazza San Pietro. This square however is late Renaissance. Connected with this is the columns you see in these scenes. They were designed by the Italian artist Bernini, and the film crew didn't even remove the statues of all the popes.
Continuity mistake: When Maximus slices the head off of his opponent, and delivers his line "Are you not entertained?" his sword begins in his left hand then it cuts to a wide shot, and it's in his right, then they cut back to a closer shot and it's back in his left hand again.
Continuity mistake: Maximus is about to be executed in the forest in Germania. Maximus kneels on the floor. The swordsman steps behind him and lifts the sword above his head to drive it down into the back of the neck of Maximus. When Maximus stands up and head-butts the swordsman the swordsman's arms are now by his side and the sword gone. The next shot shows the arms back in the air, with the sword, and Maximus grabbing the sword.