Other: 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.

Revealing: When Maximus is being taken to be executed he escapes - when he whacks the last man round the face look closely and you see he slashes about a foot away from the soldier's face.

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).

Visible crew/equipment: In addition to the gas cylinder mistake, you can also see the handbutton the rider of the chariot uses to cause the explosion attached to the chariot as he drops it.