It was filmed in Technicolor, and is based on the 1914 fantasy novel At the Earth's Core, by Edgar Rice Burroughs, the first book of his Pellucidar series. The screenplay was written by Milton Subotsky, who also produced the film along with John Dark and Max Rosenberg. The original music score was composed by Mike Vickers.
The film premiered on the 1st of September 1976.
- Doug McClure as David Innes
- Peter Cushing as Dr. Abner Perry
- Caroline Munro as Dia
- Cy Grant as Ra
- Godfrey James as Ghak
- Sean Lynch as Hoojah
- Keith Barron as Dowsett
- Bobby Parr as Sagoth Chief
- Director Kevin Connor and actor Doug McClure had previously worked together on 1974's The Land That Time Forgot, which was used in Experiment #1107. Some of the supporting cast from that earlier film also appeared in At the Earth's Core. Connor and McClure would reunite in 1977 for The People That Time Forgot.