Jason and the Argonauts is a 1963 film directed by Don Chaffey and starring Todd Armstrong, Niall MacGinnis and Honor Blackman. Special effects are by Ray Harryhausen. Bernard Herrmann did the score.
Crackle has this online, although I don't see a way to embed the video here. Watch it at this link. Youtube has it in 11 different segments here, and this is part 1:
Moria says, "This is the sort of film that the magic of special effects is all about." 1000 Misspent Hours describes it as "probably the most fondly remembered (if also the most seriously flawed) of Harryhausen’s 1960’s monster-menagerie fantasy films," primarily finding fault with the abruptness of the ending.