The Phantom Empire
When the ancient continent of Mu sank beneath the ocean, some of its inhabitant survived in caverns beneath the sea. Cowboy singer Gene Autry stumbles upon the civilization, now buried beneath his own Radio Ranch. The Muranians have developed technology and weaponry such as television and ray guns. Their rich supply of radium draws unscrupulous speculators from the surface. The peaceful civilization of the Muranians is corrupted by the greed from above, and it becomes Autry's task to prevent all-out war, ideally without disrupting his regular radio show.When the ancient continent of Mu sank beneath the ocean, some of its inhabitant survived in caverns beneath the sea. Cowboy singer Gene Autry stumbles upon the civilization, now buried beneath his own Radio Ranch. The Muranian... Read more
Starring Gene Autry, Frankie Darro, Betsy King Ross, Dorothy Christy, Wheeler Oakman, Charles K. French, Warner Richmond, J. Frank Glendon, Smiley Burnette, Peter Potter
It's a action & adventure and family movie, and has a rating of 6.2 out of 10 from Imdb which is usually fine for this kind of movie.
Watch it here
Not found streaming from Spain.