Visible crew/equipment: On the beach there's a battle charge, and in the foreground you can clearly see a set of tyre tracks from the camera vehicle preceding the charge.
Continuity mistake: When one of the siege towers is rolled over the camera, you can see one of the pushers look for the camera and move to avoid it.
Other mistake: After the Cid dies and is propped up on his horse to try to fool the enemy into thinking that he still lives, he leads his army out of the fortress and attacks the offenders. Just after he comes out of the gates the horse stops and there is a shot of the Cid on his horse being almost silhouetted against the sun. If you watch carefully you will see Charlton Hestons' head move slightly and look towards the direction of the enemy.Even though the horse turns slightly under him the Cid's' head keeps looking in their direction. Obviously this would be impossible if he was dead, and even more so when you remember that his body was supposed to have been tied tightly to a support so that he would sit upright when on top of the horse.