It’s essentially a silly Victorian adventure movie starring Doug McClure as a heroic explorer, partnered with Peter Cushing, who provides a performance reminiscent of his "Doctor Who" work, playing the scientist responsible for a remarkably uninspired device intended to journey into the Earth's core. Inside, they find captives under the control of enormous, irate, telepathic penguins. Drawing from an Edgar Rice Burroughs story, the special effects are quite poor, and so is much of the film itself. However, it wasn’t terrible; I found it to be a genuinely enjoyable movie as a child.

Source on TMDB