Revealing mistake: During the chariot race, where the contestants are riding towards the screen, tyre tracks from the camera vehicle are clearly visible imprinted in the sand. (00:20:50)
Revealing mistake: When one of the ships collides with the other, you can clearly see that the rowers being hit are dummies. (01:19:00)
Revealing mistake: There is a hex bolt holding the spikes to the chariot wheel hub. (00:14:10)
Revealing mistake: When the slaves are walking through the desert on their route to Tyros, in several scenes it's obvious that a double is standing in for Charlton Heston as Ben-Hur.
Revealing mistake: When Stephen Boyd is showing off the spikes on his chariot wheel you can see welding beads along the projecting hub.
Revealing mistake: During the race Judah runs into the remains of another chariot and almost falls off the cart. You can see that the guy who is doing the handstand on the railing is a stuntman. (00:26:15)
Revealing mistake: The chariot race is about to begin, and Messala arrives late. As he's backing his team into position, look at the left side of the left-most horse's neck. You can see the reins rubbing the black dye off. (Solid black horses are *extremely* rare).
Revealing mistake: During the naval battle, the same footage of a sinking galley is used several times, apparently to represent the sinking of several galleys.
Revealing mistake: When Miriam, Esther and Tirzah find shelter from the storm in a cave, the storm is violent and the wind is howling, but the trees visible in the background are barely swaying.
Revealing mistake: When Judah and Messala hurl their spears into the wooden beam, the projectiles follow very straight paths all the way across the room to their targets, whereas due to gravity they'd really travel curved paths, practically parabolic, requiring a skilled thrower to aim above the target. What's revealed here is that the spears were rigged to slide on thin wires, to assure that they'd hit the target on cue.
Revealing mistake: During the chariot race, when they're about to make a left turn around a corner, the people wave their arms. Right when they're making the turn, the arms move awkwardly fast, revealing the scene was speeded-up. (02:48:37)