George Pal was unhappy with the script but was forced to begin production before it had been polished due to an impending writers' strike. The strike occurred during production, which stopped any rewrites.
When Columbus discovered America, a series of mysteries arose to confound the scholars of Europe. Here are two continents, completely isolated from each other, yet they simultaneously developed similar cultures. For example, the Mayans measured time...
When Antillia steals the boat, the background shows the sea with normal waves. When Demetrios swims out to the boat the water is extremely calm. This also gives away the fact that the shot of Hall swimming was done in a studio tank.
For once in his life, Paul Frees gets an on-screen credit for a voice-over job, the narration in the opening and closing sequences. Strangely, he is billed not in the cast list, but in the technical credits.
When originally released theatrically in the UK, the BBFC made cuts to secure a 'A' rating.