Mysterious Island (1973)

Original title: L'Île Mystérieuse

During the American Civil War, five prisoners of war manage to escape in a balloon. They are driven far across the sea to an unknown island, far from civilization. The legendary captain Nemo (world star Omar Sharif), who is trapped in a huge underground cave with his submarine Nautilus, watches the group. When the stranded people are discovered by pirates, Nemo helps them with a host of his super technology...