Continuity mistake: When Kirk Douglas smashes through the chapel window near the end of the film, you can clearly see that the window isn't stained glass - it's colored paper. Or perhaps papier-mache of some sort.
Continuity mistake: When Eric and the others are making their escape in the boat, the ladies are in front at first. Later on they are behind the men as they all row the boat.
Continuity mistake: When Kirk Douglas climbs the axes thrust against the drawbridge, he is unarmed. After he lowers the bridge, his sword is strapped across his back, only to reappear in the following shots on his belt.