H.G. Wells' Astounding Adventure In DYNAMATION!
First Men In The Moon(1964) was filmed using "Dynamation," which Ray Harryhausen fans know is a term he used to describe his distinctive hybrid stop-motion/live-action special effects. There's a great article on Harryhausen's official website about the process, and I'd encourage you to all check it out.
As a side note, tomorrow's Sci-Fi Poster Art of the Day also features a film with the word "First" and a reference to a celestial body in the title. Any guesses?
The poster for First Men In The Moon is a good one, featuring tons of detail in the sub-lunar-surface world. Click through for a look at the poster, as well as a trailer for the film. If you're like me, the trailer will have you exclaiming "WE'RE OFF!" for the rest of the day.