The visuals are absolutely beautiful, and they are apparently achieved by a clever combination of animated drawings combined with live actors, stop-motion animation and sets that are painted so that they look much like from an animated movie. Combined by Jules Verne's own unique versions of airplanes and submarines and Karel Zeman's good directing results in a very well done and convincing visual style that manages to effectively hold one's attention until the end of the movie.
There are some problems as well, one of the underwater scenes at the end takes maybe needlessly lot of time for example, as the story in the first part of the movie is rushed through quite quickly. None of this matters much though since the movie is always highly enjoyable. A gem that deserves to be more well known for today's audiences as well. A recommended movie for the whole family.