Dr. Abner Perry, a British Victorianscientist, and his US financier David Innes make a test run of their Iron Moledrilling machine in a Welsh mountain, but end up in a strange underground labyrinth ruled by a species of giant telepathic flying reptiles, the Mahars, and full of prehistoric monsters and cavemen. They are captured by the Mahars, who keep primitive humans as their slaves through mind control. David falls for the beautiful slave girl Princess Dia but when she is chosen as a sacrificial victim in the Mahar city, David and Perry must rally the surviving human slaves to rebel and not only save her but also win their freedom.
The film was made following the success of The Land That Time Forgot. Kevin Connor later recalled, "we tried to get the beasts bigger so as to interact better with the actors – more one on one. We had a somewhat bigger budget thanks to the success of ‘Land.’ The beasts were specially designed so that small stunt guys could work inside the suits in a crouched position and on all-fours. Needless to say it was very cramped and the stunt guys had to take frequent breathers. Some worked better than others – but we were experimenting and trying something different."
Reception
The film was popular, becoming the 18th most profitable British film of 1976. Amongst contemporary critics, however, The New York Times was not impressed: "All the money used to make 'At the Earth's Core' seems to have been spent on building monsters with parrotlike beaks that open, close, and emit a steady squawling as if someone were vacuuming next door. Close up, the monsters look like sections of rough concrete wall and the decision to film them in closeup is only one example of the total lack of talent or effort with which the picture is made...the movie is a kind of no-talent competition in which the acting, the script, the direction and the camera-work vie for last place." More recently, in more positive vein, BFI Screenonline said, "Extravagant, colourful and thoroughly preposterous, At the Earth's Core is utterly without pretension but has the exuberant charm of the best of its decade." The film was featured in the season finale of the revived Mystery Science Theater 3000, the show's eleventh season overall, released on April 14, 2017 through Netflix.