The Mole People (1956)

On an archaeological dig in Asia, Dr. Roger Bentley finds a cuneiform tablet referring to an ancient society, the Shadow Dynasty, that was destroyed. An earthquake soon after reveals an ancient artifact and the scientists discover the ruins of an ancient temple world on a remote mountain site. It leads them to an underground world, lost in time, where people have adapted to low light. The High Priest Elinu doesn't welcome the presence of the new arrivals and wants them eliminated.