Factual error: Before the spectacular chariot race, we have the "Parade of the Charioteers." Around the arena you see classical statues. They are just props, they do not influence the storyline at all, they are just dotted around the set to remind us that we are in the Roman Empire. All the statues are just plain white stone. Archaeological research shows that the great Greek and Roman sculptors always painted their sculptures. Skin, clothes, eyes, hair, were all carefully painted to make the statues look 100% lifelike. In the next thousand years the paint wore away, and now, when you go to a museum and look at Greek and Roman sculptures you only see plain stone figures. Yet in ancient Greece and Rome all those statues were elaborately painted. This error applies not just to Ben Hur but probably every classical epic film ever made.
Factual error: The circus maximus was built in such a way as to allow the entire track to be visible to the spectators. This is not the case in Ben Hur.
Factual error: Emperor Tiberius of Rome was a reclusive and vicious tyrant by 26AD when "Ben Hur" is set. Furthermore, by that time, he had retired to Capri and was rarely in Rome. In the movie, he's the picture of Regal benevolence, basking in the love of the crowds and showering glory on Arrias in victory. In real-life that never would have happened. Tiberius' Governor Sejanus would have presided over Arrias' triumph, not Tiberius. (01:23:00 - 01:26:00)
Factual error: When Judah is being led to the galleys after Jesus give him some water you see hills in the background, and a highway is going through them. (01:05:10)