one of George Pal's best!
this is one great movie. I saw it on the re-release in probably 1978 (on a double bill with When Worlds Collide (1951) and that was a very cool evening for me and my brother. imDb says it was released in August 1977, but it probably didn't make it's way to Colorado for some time. George Pal was the producer, and his output of fantastic films was really only surpassed by Eiji Tsuburaya.