During World War I, a German U-boat sinks a British ship and takes the survivors on board. After it takes a wrong turn, the submarine takes them to the unknown land of Caprona, where they find dinosaurs and neanderthals. –IMDb
One of the better film adaptations of Edgar Rice Burroughs' pulp adventure stories is an entertaining B-movie. A handsome Amicus production, though the low-budget special effects are predictably lackluster (there's a scene involving a pterodactyl that laughably just doesn't cut it). Not great cinema by any means, but a lot of fun.