Continuity mistake: When John baptizes Jesus, Jesus' hair is dripping water onto his shoulders as seen from the front. As seen from the back, there's no dripping at all.
Continuity mistake: When they are trying to break the castle's door, it is broken differently outside and inside.
Continuity mistake: In the scene when Richard Harris and Kirk Douglas parachute back into Norway, there is a white parachute blowing in the wind. Kirk Douglas goes to collect it, but there are footprints already in the snow where they have previously filmed a retake. (00:27:00)